JP3145097B2 - Dry etching equipment - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry etching apparatus, and particularly to a low damage, high selection,
The present invention relates to a dry etching apparatus that enables highly anisotropic etching.

[Conventional technology]

In dry etching of a semiconductor device manufacturing process, the selectivity is high, that is, the etching rate of a thin film to be etched is much higher than the etching rate of a base material or a mask material such as a photoresist, and the anisotropy is high, that is, The etching rate in the vertical direction on the thin film surface to be etched is much larger than the etching rate in the horizontal direction, so-called undercut is negligible in the etched shape. It is essential that the change be very small. The demand for such high selectivity, high anisotropy, and low damage of etching has been increasing with the improvement of the degree of integration of devices.

Conventional dry etching equipment uses high-frequency discharge plasma such as RF discharge or microwave discharge, and is widely used in the semiconductor device manufacturing process as a device that has both fine workability and mass productivity. .

Fig. 6 shows, for example, Kazuo Akashi, Shuzo Hattori, Osamu Matsumoto,
Plasma Processing ”(Nikkan Kogyo Shimbun, Tokyo, Showa
This is a cross-sectional view showing the outline of a conventional dry etching apparatus using RF discharge plasma shown in Chapter 10, "Basics of Plasma Etching" (authored by Yukio Yasuda).

In the drawing, reference numeral 1 denotes a substrate to be etched, 2 denotes a first parallel plate electrode on which the substrate 1 is mounted, 3 denotes a second parallel plate electrode disposed opposite to the parallel plate electrode 2, 4 Is a plasma reaction vacuum vessel in which the first parallel plate electrode 2 and the second parallel plate electrode 3 are installed, 5 is a vacuum exhaust means for exhausting the gas inside the vessel 4, and 6 is the first parallel plate. RF power applying means for applying RF power between the electrode 2 and the second parallel plate electrode 3, a gas cylinder 7 filled with the etching gas A supplied into the plasma reaction vessel 4, and a gas cylinder 8 7 to the above container 4
Gas flow rate control means for adjusting the flow rate of the etching gas into the chamber, 9 is a pressure gauge for monitoring the pressure of the etching gas in the vessel 4, and 10 is the pressure gauge of the first parallel plate electrode 2 and the second parallel plate electrode 3. This is the RF discharge plasma generated between them.

The material to be etched, the base material,
As the photoresist, for example, polycrystalline silicon (Poly
crystalline Si), silicon oxide (SiO ₂ ), PMMA (Poly
[Methyl Methacrylate]) is used, and as the etching gas A filled in the gas cylinder 7, for example, a mixed gas of chlorine (Cl ₂ ) and argon (Ar) is used. The frequency of the RF power applying means 6 is, for example, 13.5
6 MHz.

 Next, the operation will be described.

First, after the substrate 1 to be etched is placed on the first parallel plate electrode 2 in the plasma reaction vacuum vessel 4, the inside of the vessel 4 is evacuated by the vacuum exhaust means 5. Subsequently, the flow rate of the etching gas A supplied from the gas cylinder 7 into the container 4 is adjusted and set by the gas flow rate control means 8, and the gas pressure in the container 4 is monitored while the gas pressure in the container 4 is monitored by the pressure gauge 9. The etching speed is adjusted to set the etching gas pressure in the container 4.

Next, when RF power is applied between the first and second parallel plate electrodes 2 and 3 by the RF power applying means 6, the etching gas in the plasma reaction vessel 4 is subjected to a high frequency glow discharge generated between the electrodes 2 and 3. , And the reactive weakly ionized plasma 10 is generated. The substance on the substrate 1 is etched by the resulting neutral molecular radicals and atomic ions or neutral molecular radicals and molecular ions composed of a combination thereof.

Here, for example, chlorine (C
l ₂ ) and a mixed gas of argon (Ar), Cl is used as a neutral atomic radical, Cl ⁺ and Ar ⁺ are used as atomic ions,
And Cl ₂ ⁺ is generated as a molecular ion. In this case, there are no molecular radicals. The etching gas pressure in the plasma reactor 4 is 0.01 to 1 Torr, and the gas density is 3 × 10 ^{14 to} 3 × 10 ¹⁶ cm ⁻³ , and the plasma density is
It is about 10 ⁹ -10 ¹¹ cm ^-3 .

FIG. 7 is a schematic diagram for explaining a mechanism in which a substance on a substrate placed on an electrode in plasma is etched in an etching apparatus using the conventional RF discharge plasma. In such a discharge plasma, there are many kinds of neutral atoms and molecules with various energies, their ions, and electrons and photons (radiation) of various energies. The contributing particles are atoms and molecular ions and neutral atoms and molecular radicals in a space charge region (sheath) formed near the substrate.

In this sheath region, positive ions having a positive charge tend to be accelerated in the direction of the substrate by a sheath potential (plasma potential + self-bias potential of the electrode) of about 100 V to 1 kV and vertically incident on the substrate surface. The radicals do not respond to the sheath potential, and are isotropically incident on the substrate surface by thermal random motion of about 500 to 1000 ° K.

In such a dry etching apparatus, the selectivity of etching, that is, the ratio of the etching rate of a thin film to be etched to the etching rate of a base material or a mask material such as a photoresist is mainly determined by a chemical reaction of a neutral radical with respect to each substance. Although it is obtained by the difference in reactivity, chemical etching using only neutral radicals isotropically incident on the substrate surface is isotropic.

On the other hand, the etching anisotropy, that is, the ratio of the etching rate in the vertical direction to the thin film surface of the thin film to be etched and the etching rate in the horizontal direction, is mainly accelerated by the sheath potential, and the ions of the ions which are vertically incident on the substrate surface. Physical sputtering by ions, which is obtained by the direction of motion relative to the surface, is non-selective for each substance and causes considerable damage to the surface layer of the thin film to be etched. In reality, the etching of the substance on the substrate proceeds by a competition process between these neutral radicals and ions, which is called an ion assist process.

[Problems to be solved by the invention]

The conventional dry etching apparatus using discharge plasma places the substrate to be etched on the electrode in the plasma as described above, and accelerates the substrate by a sheath potential in a space charge region (sheath) formed near the substrate. Since it is configured to obtain anisotropy of etching only by the directionality of the movement of ions which are perpendicularly incident on the surface, in order to increase the anisotropy of etching, the sheath potential and, consequently, the incident energy of the ions into the substrate are required. As a result, the higher the anisotropy is to be obtained, the lower the selectivity is and the more the damage is increased.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a dry etching apparatus capable of realizing etching that simultaneously satisfies both ultra-high anisotropy and ultra-high selectivity and extremely low damage. Aim.

[Means for solving the problem]

The dry etching apparatus according to the invention of claim 1 of the present application is a dry etching apparatus for introducing a source gas and etching a material to be etched, wherein the dry etching apparatus has a jet nozzle for jetting a generated gas, and the atomic molecules of the source gas are provided. And a first vacuum chamber for introducing the plasma into the interior through the ejection nozzle and supersonic expanding the plasma to form a supersonic free jet. Having a skimmer for extracting a supersonic molecular flow from a supersonic free jet of the plasma, and a second vacuum chamber for introducing the supersonic molecular flow, and taken out of the second vacuum chamber. The supersonic molecular flow of plasma is blown onto the material to be etched.

Further, the dry etching apparatus according to the invention of claim 2 of the present application is a dry etching apparatus for etching a material to be etched by introducing a raw material gas, comprising a jet nozzle for jetting a generated gas, A discharge chamber for generating plasma by ionizing molecules, and a first vacuum chamber for introducing the plasma into the interior through the ejection nozzle and supersonic expansion to form a supersonic free jet And a skimmer for extracting a supersonic molecular flow of the plasma from the supersonic free jet of the plasma; a second vacuum chamber for introducing the supersonic molecular flow; and a skimmer taken out of the second vacuum chamber. Charged ion removing means for removing ions and electrons from the supersonic molecular flow of the plasma to form a supersonic molecular flow of a neutral atomic molecular gas, wherein the supersonic molecular flow of the neutral atomic molecular gas is Suffered In which was set to blow the etching material.

Further, the dry etching apparatus according to the invention of claim 3 of the present application is a dry etching apparatus using discharge of reactive gas atomic molecules, wherein a discharge chamber for generating plasma, and the plasma generated in the discharge chamber are supersonic expanded. The two-dimensional nozzle having a rectangular slit-shaped opening
Through the nozzle from the discharge chamber and the first
A two-dimensional skimmer having a rectangular slit-shaped opening section and a second vacuum chamber for extracting a supersonic molecular flow from a supersonic free jet of plasma formed by supersonic free expansion in a vacuum chamber, The supersonic molecular flow of the plasma taken out from the first vacuum chamber through the skimmer into the second vacuum chamber is blown onto the substrate to be etched to perform the etching.

Further, the dry etching apparatus according to the invention of claim 4 of the present application is a dry etching apparatus using discharge of reactive gas atomic molecules, wherein a discharge chamber for generating plasma, and the plasma generated in the discharge chamber are supersonic expanded. The two-dimensional nozzle having a rectangular slit-shaped opening
Extracting a supersonic molecular flow from a supersonic free jet of plasma formed by supersonic free expansion from the discharge chamber through the nozzle into the first vacuum chamber, the opening having a rectangular slit shape. A two-dimensional skimmer and a second vacuum chamber,
Means for removing charged particles from a supersonic molecular flow of the plasma taken out of the first vacuum chamber through the skimmer into the second vacuum chamber, wherein the supersonic wave of the plasma taken out of the second vacuum chamber is provided. The supersonic molecular flow of neutral atomic molecular gas from which ions and electrons have been removed from the sonic molecular flow by the charged particle removing means is blown onto the substrate to be etched to perform etching.

The dry etching apparatus according to the invention of claim 5 of the present application is the dry etching apparatus according to claim 3 or 4, wherein the position of the substrate to be etched is a sheet shape having a rectangular cross section perpendicular to the flow. The etching is performed while relatively moving the supersonic molecular flow as a beam in the direction of the short side.

Further, the dry etching apparatus according to the invention of claim 6 of the present application is a dry etching apparatus using discharge of reactive gas atomic molecules, wherein a discharge chamber for generating plasma and a plasma generated in the discharge chamber are supersonic expanded. A nozzle, a first vacuum chamber, and a skimmer for extracting a supersonic molecular flow from a supersonic free jet of plasma formed by supersonic free expansion through the nozzle from the discharge chamber and into the first vacuum chamber. A second vacuum chamber, wherein a reactive gas and a light element gas such as helium or hydrogen are introduced into the discharge chamber to ionize the mixed gas, and the mixed gas is ionized from the first vacuum chamber through the skimmer. The supersonic molecular flow of the plasma taken out into the vacuum chamber of No. 2 is blown onto the substrate to be etched to perform the etching.

Further, the dry etching apparatus according to the invention of claim 7 of the present application is a dry etching apparatus using discharge of reactive gas atomic molecules, wherein a discharge chamber for generating plasma, and the plasma generated in the discharge chamber are supersonic expanded. A nozzle, a first vacuum chamber, a skimmer for extracting a supersonic molecular flow from a supersonic free jet of plasma formed by supersonic free expansion from the discharge chamber through the nozzle into the first vacuum chamber. A vacuum chamber, and means for removing charged particles from a supersonic molecular flow of plasma taken out of the first vacuum chamber through the skimmer into the second vacuum chamber. And introducing a light element gas such as helium or hydrogen to ionize the mixed gas and remove the charged particles from the supersonic molecular flow of the plasma taken out into the second vacuum chamber. The supersonic molecular flow of neutral atoms and molecules gases removed ions and electrons by means, in which to perform the etching by spraying the etching target substrate.

The dry etching apparatus according to the invention of claim 8 of the present application is the dry etching apparatus according to claim 6 or 7, wherein the discharge chamber is divided into two chambers, and a light element gas such as helium or hydrogen is introduced. A first chamber for ionizing the light element gas and a second chamber for introducing the plasma generated by the ionization, further introducing the reactive gas, and mixing the two gases are provided.

[Action]

In the invention of claim 1 of the present application, with the above-described configuration, the plasma generated by the discharge is supersonic expanded in a vacuum, and the gas temperature is extremely low, that is, heavy atoms such as neutral atomic molecules and ions. A supersonic molecular flow of plasma, in which the thermal motion velocity of the particles is extremely small and the interaction between heavy particles is negligible, is generated, and the supersonic molecular flow of the plasma is blown onto the substrate to be etched, so that the plasma ions and Neutral atomic molecules are incident perpendicularly to the substrate surface as a low-temperature low-energy particle beam. In this case, the velocity component of the ions and neutral radicals in the horizontal direction with respect to the substrate surface is extremely small compared to the incident velocity in the vertical direction,
Also, the incident energy is much smaller than the physical sputter threshold. For this reason, in this device, anisotropic chemical etching by neutral radicals governs the etching process of the substance on the substrate, and not only ultra-high anisotropy but also ultra-high selectivity and extremely low damage Satisfactory etching becomes possible.

Further, in the invention of claim 2 of the present application, by configuring as described above, ions and electrons are removed from the supersonic molecular flow of the plasma, and the gas temperature is extremely low.
In other words, the supersonic molecular flow of neutral atomic molecular gas, in which the thermal motion velocity of neutral atomic molecules is extremely small and the interaction between particles is negligible, is taken out and this supersonic molecular flow of neutral atomic molecular gas is blown onto the substrate to be etched. As a result, the neutral atom molecules are vertically incident on the substrate surface as a low-temperature low-energy particle beam.

Therefore, in this case, the etching of the substance on the substrate proceeds only by the anisotropic chemical etching by the neutral radical, and the etching which satisfies the ultra-high anisotropy, the ultra-high selectivity and the extremely low damage simultaneously can be performed. Not only
Electrostatic breakdown due to charge-up of the substrate to be etched can be prevented.

In the invention of claim 3 of the present application, by configuring as described above, first, the plasma generated by the discharge is supersonic expanded in a vacuum, and the gas temperature is extremely low, that is, neutral atom molecules or ions. Since the thermal motion speed of heavy particles is extremely low, the interaction between heavy particles is negligible and a supersonic molecular flow of plasma is generated, and this supersonic molecular flow of plasma is blown onto the substrate to be etched. Ions and neutral atomic molecular radicals are vertically incident on the substrate surface as a low-temperature low-energy particle beam. In this case, the velocity component of the ions and neutral radicals in the horizontal direction with respect to the substrate surface is extremely small as compared with the incident velocity in the vertical direction, and the incident energy is much smaller than the physical sputtering threshold. For this reason, in this dry etching apparatus, the anisotropic chemical etching by neutral radicals controls the etching process of the substance on the substrate, so that not only ultra-high anisotropy but also ultra-high selectivity and extremely low damage Can be satisfied at the same time.

In the invention of claim 4 of the present application, by employing the above-described structure, ions and electrons of charged particles are removed from the supersonic molecular flow of the plasma, and the gas temperature is extremely low, that is, neutral atomic molecules The supersonic molecular flow of neutral atomic molecular gas, whose thermal motion velocity is extremely small and the interaction between particles is negligible, was taken out, and this supersonic molecular flow of neutral atomic molecular gas was blown onto the substrate to be etched. On the other hand, neutral atomic molecular radicals are vertically incident on the substrate surface as a low-temperature low-energy particle beam. In this case, the velocity component of the neutral radical in the horizontal direction with respect to the substrate surface is extremely small as compared with the incident velocity in the vertical direction, and the incident energy is much smaller than the physical sputtering threshold. Therefore, the etching of the substance on the substrate proceeds only by the anisotropic chemical etching by the neutral radical, and it is possible to perform the etching which simultaneously satisfies the ultra-high anisotropy, the ultra-high selectivity and the ultra-low damage property. In addition, electrostatic destruction due to charging (charge-up) of the substrate to be etched by charged particles can be prevented.

Further, in the invention of claim 5 of the present application, by configuring as described above, in the supersonic molecular flow of the plasma and the supersonic molecular flow of the neutral atomic molecular gas,
Since a two-dimensional nozzle and a skimmer having a rectangular slit-shaped cross section are used for their generation, the cross-sectional shape perpendicular to the flow is a rectangular slit. Therefore, the position of the substrate to be etched is relatively set with respect to the supersonic molecular flow,
Since the etching is performed while moving in the short side direction of the cross section, it is possible to etch a large-diameter substrate while simultaneously satisfying ultra-high anisotropy, ultra-high selectivity and extremely low damage.

Further, in the invention of claim 6 of the present application, by configuring as described above, first, a reactive gas and a light element gas such as helium or hydrogen are introduced into the discharge chamber to generate plasma of the mixed gas, The plasma is supersonic expanded in a vacuum, and the gas temperature is extremely low, that is, the thermal motion of heavy particles such as neutral atomic molecules and ions is extremely small, and the supersonic molecular flow of plasma in which the interaction between heavy particles can be ignored Is generated, and the supersonic molecular flow of the plasma is blown onto the substrate to be etched, so that the plasma ions and neutral atomic molecular radicals are vertically incident on the substrate surface as a low-temperature low-energy particle beam. In this case, the velocity component of ions and neutral radicals in the horizontal direction with respect to the substrate surface is extremely small as compared with the incident velocity in the vertical direction, and the incident energy is much smaller than the physical sputtering threshold. Also, when the mixing ratio of the reactive gas to the light element gas is reduced, the incident velocity of ions and neutral radicals on the reactive gas in the direction perpendicular to the substrate surface is almost equal to the incident velocity of atomic molecules on the light element gas. Up to the value. For this reason, in the present dry etching apparatus, the more anisotropic chemical etching by fast neutral radicals governs the etching process of the substance on the substrate, and not only the ultra-high anisotropy but also the ultra-high selectivity Etching that simultaneously satisfies the ultra-low damage property can be realized at a high speed.

Further, in the invention of claim 7 of the present application, with the above configuration, ions and electrons of charged particles are removed from the supersonic molecular flow of the plasma, and the gas temperature is extremely low, that is, neutral atomic molecules The supersonic molecular flow of neutral atomic molecular gas, whose thermal motion velocity is extremely small and the interaction between particles is negligible, is taken out, and this supersonic molecular flow of neutral atomic molecular gas is blown onto the substrate to be etched. Therefore, the neutral atomic molecular radicals are vertically incident on the substrate surface as a low-temperature low-energy particle beam. In this case, the velocity component of the neutral radical in the horizontal direction with respect to the substrate surface is extremely small as compared with the incident speed in the vertical direction,
Also, the incident energy is much smaller than the physical sputter threshold. In addition, when the mixing ratio of the reactive gas to the light element gas is reduced, the incident velocity of neutral radicals on the reactive gas in the direction perpendicular to the substrate surface becomes substantially equal to the incident velocity of atomic molecules on the light element gas. Faster. Therefore, the etching of the substance on the substrate proceeds only by the more anisotropic chemical etching due to the fast neutral radical, and the high speed which satisfies ultra-high anisotropy, ultra-high selectivity and ultra-low damage simultaneously. Not only can etching be performed, but also electrostatic destruction due to charging (charge-up) of the substrate to be etched by charged particles can be prevented.

In the invention of claim 8 of the present application, by configuring as described above, the discharge chamber is divided into two chambers, and a light element gas such as helium or hydrogen is introduced to ionize the light element gas. Since the first chamber and the second chamber into which the ionized gas flows and into which the reactive gas is further introduced to mix the two gases are provided, the ionization and dissociation of the reactive gas atom molecules are not direct discharges, Interaction with light element gas plasma generated by direct discharge, that is, light element gas atom molecules generated or excited by ionization or dissociation due to discharge or collision of reactive gas atom molecules with electrons of plasma, occurs.

Therefore, the amount of neutral radicals generated by the dissociation of reactive gas atom molecules is greater than in the case of direct discharge,
In addition, the degree of corrosion and damage of the discharge chamber due to the direct discharge of the reactive gas is reduced. The supersonic molecular flow of the plasma extracted from the plasma thus generated, or the supersonic molecular flow of the neutral atomic molecular gas obtained by removing ions and electrons from the supersonic molecular flow of the plasma by the above-described charged particle removing means. Since etching is performed by spraying on the substrate to be etched, etching that can simultaneously satisfy ultra-high anisotropy, ultra-high selectivity, and extremely low damage can be obtained at a higher speed, and deterioration of the discharge chamber is suppressed. Life can be extended.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a main part showing a configuration of a dry etching apparatus according to a first embodiment of the present invention. In the figure,
21 is a reactive gas discharge chamber, 22 is a first vacuum chamber disposed adjacent to the discharge chamber 21, 23 is a second vacuum chamber disposed adjacent to the first vacuum chamber 22, 24 Is the second vacuum chamber 23
, A third vacuum chamber having an electrode 2 for mounting the substrate 1 to be etched, 26 a nozzle installed at one end 25 of the reactive gas discharge chamber 21, and 27 a first nozzle A first partition partitioning the vacuum chamber 22 from the second vacuum chamber 23;
28 is a skimmer installed on the first partition 27, 29 is a second partition separating the second vacuum chamber 23 and the third vacuum chamber 24, and 30 is installed on the second partition 29. Collimator.

Reference numeral 31 denotes first vacuum exhaust means for exhausting the first vacuum chamber 22, and reference numerals 32, 33 denote the second and third vacuum chambers 23, 33, respectively.
24, a second and third vacuum exhaust means for exhausting gas; 7, a gas cylinder filled with an etching gas A to be supplied into the reactive gas discharge chamber 21;
Gas flow rate control means for adjusting the flow rate of the etching gas into the chamber 21; 9 is a pressure gauge for monitoring the etching gas pressure in the discharge chamber 21; 11 to 13 are the first to third vacuum chambers 22; The first to third vacuum gauges for monitoring the degree of vacuum in to 24, a high-frequency induction coil 14 provided around the reactive gas discharge chamber 21, and a RF power applied to the coil 14 RF power application means.

Reference numeral 10 denotes an RF induced discharge plasma generated in a portion of the discharge chamber 21 where the coil 14 is installed.
Is introduced into the first vacuum chamber 22 through the nozzle 26, where a supersonic free jet of plasma formed by supersonic expansion, E, passes from the supersonic free jet D of the plasma through the skimmer 28. The second vacuum chamber 23
The supersonic molecular flow J of the plasma extracted inside the supersonic molecular flow E of the plasma that has passed through the collimator 30 and flowed into the third vacuum chamber 24 out of the supersonic molecular flow E of this plasma The substrate 1 to be etched is placed on the electrode 2 in the third vacuum chamber 24 so as to face the supersonic molecular flow J of the plasma.

The nozzle 26, the skimmer 28 and the collimator 30 are arranged in a straight line, and the supersonic free jet D in the first vacuum chamber 22, the supersonic molecular flow E in the second vacuum chamber 23, And on the same axis as the central axis of the supersonic molecular flow J in the third vacuum chamber 24.

Further, as a material to be etched, a base material, and a photoresist on the substrate 1 to be etched, for example, polycrystalline silicon, silicon dioxide, and PMMA are used as in the conventional example, and the etching gas A filled in the gas cylinder 7 is also used. For example, a mixed gas of chlorine and argon is used as in the conventional example. Also, the frequency of the RF power applying means 6 is
For example, 13.56 MHz as in the conventional example.

Next, the operation of the dry etching apparatus according to the above embodiment will be described.

First, the first to third vacuum chambers 22 to 24 are evacuated by the first to third vacuum exhaust means 31 to 33, respectively, and the reactive gas discharge chamber 21 and the first to third vacuum chambers 22 to 24 is set to a predetermined degree of vacuum.

Next, the etching gas A is introduced from the gas cylinder 7 into the reactive gas discharge chamber 21 through the gas flow rate control means 8 while the first to third vacuum exhaust means 31 to 33 are evacuated,
Further, the gas pressure in the discharge chamber 21 is set by monitoring the gas pressure in the discharge chamber 21 by the pressure gauge 9 and adjusting the flow rate of the etching gas by the gas flow rate control means 8.

Subsequently, the high frequency induction coil 14 is
When RF power is applied to the etching gas, the etching gas in the discharge chamber 21 is ionized by RF-induced glow discharge or arc discharge, and the reactive weakly ionized plasma 10 is generated. Here, the pressure in the discharge chamber 21 is about 10 ² to 10 ³ Torr, and the temperature is 10 ³ to 10 ⁴ Torr.
Degree, and the pressure is indicated by the pressure gauge 9.

The plasma of the etching gas A generated in the reactive gas discharge chamber 21 passes through the nozzle 26 and is introduced into the first vacuum chamber 22, where it expands at supersonic speed to form a supersonic free jet D. . The opening diameter of the nozzle 26 is, for example, about 1 mm, and the degree of vacuum in the first vacuum chamber 22 is maintained at about 10 ^-3 to 10 ^-2 Torr, which is indicated by the first vacuum gauge 11. You.

As shown in detail in FIG. 2, the supersonic free jet D has a supersonic free-expansion flow region called a zone of silence, a barrel-shaped shock wave (Barrel Shock) and a Mach that surrounds the zone of silence. It is characterized by a shock wave called a Mach Disk. Note that a jet boundary (Jet Boundary) exists around the barrel-shaped shock wave, and a reflected shock wave (Reflected Shock) exists downstream of the Mach disk. In the supersonic free expansion flow in the quiet region, as the gas moves downstream along the center axis of the flow, the density and temperature of the plasma, that is, the plasma is formed by the supersonic free expansion of the gas, in other words, the adiabatic expansion of the gas. The density and temperature of the neutral molecules, ions, and electrons that move are reduced.
Therefore, the frequency of collision between plasma particles decreases and the degree of ionization freezes, but the flow velocity increases. Further, the gas temperature of the plasma, that is, the temperature of heavy particles such as neutral atomic molecules and ions is extremely low at several degrees or less in absolute temperature, and the temperature of heavy particles is about 10 times or more downstream of the opening diameter of the nozzle 26 from the nozzle 26. The collision frequency between them is almost infinitesimal. However, the electron temperature of the plasma as the temperature of the heavy particles without lowering is stopped about 10 ³ times.

In such a supersonic free jet D of plasma, the supersonic free expansion is sufficiently developed along the central axis of the flow, the gas temperature of the plasma is sufficiently reduced, and the heat of heavy particles such as neutral atomic molecules and ions is generated. The skimmer 28 is arranged at a position where the movement speed is extremely small and the interaction between the heavy particles can be ignored. Specifically, a skimmer 28 is installed on the first partition wall 27, and the opening of the skimmer 28 has a shape that does not disturb the upstream of the supersonic free jet D, and the opening diameter is the opening diameter of the nozzle 26. Of 2
Approximately three times or less. A portion of the supersonic free jet D formed by the skimmer 28 in the quiet region of the supersonic free jet D near the central axis is extracted as a supersonic molecular flow E into the second vacuum chamber 23. Is done. The degree of vacuum in the second vacuum chamber 23 is maintained at about 10 ⁻⁶ to 10 ⁻⁵ Torr, and this is displayed by the second vacuum gauge 12.

By the way, the state of the supersonic free jet D of the plasma, for example, changes in physical quantities such as the size of the quiet region and the plasma gas density, temperature, and flow velocity along the central axis of the flow depend on the shape of the nozzle 26 and It is defined by various conditions such as the opening diameter, the pressure in the reactive gas discharge chamber 21 and the degree of vacuum in the first vacuum chamber 22. Therefore, the skimmer 28 is moved from the quiet region of the supersonic free jet D of plasma formed in the first vacuum chamber 22.
Supersonic molecular flow E into the second vacuum chamber 23 through
In order to keep the extraction optimal in response to changes in various conditions, it is preferable to provide a mechanism for continuously varying the distance between the nozzle 26 and the skimmer 28. In this embodiment, this mechanism is provided.

Next, referring to FIG. 3, such a nozzle 26-skimmer 28
An example of the mechanism for continuously varying the distance will be described. As shown in the figure, in this mechanism, the discharge chamber 21 is connected to the first vacuum chamber 22 by, for example, a bellows 41, and the length of the bellows 41 is expanded or contracted to make the reactive gas discharge chamber 21 an arrow shown in FIG. By moving in the α and β directions, the distance between the nozzle 26 and the skimmer 28 can be continuously changed. Therefore, the supersonic molecular flow E of plasma can be optimally extracted from the supersonic free jet D of plasma whose state changes in response to changes in various conditions.

In the supersonic molecular flow E of the plasma extracted in the second vacuum chamber 23 in this manner, the gas temperature of the plasma is extremely low as a few degrees or less in absolute temperature, that is, heavy particles such as neutral atomic molecules and ions. Has a very small thermal velocity, and the interaction between heavy particles can be neglected. The supersonic molecular flow E of the plasma having such characteristics passes through the collimator 30 provided on the second partition 29 and flows into the third vacuum chamber 24. Here, the opening diameter of the collimator 30 is equal to or less than the opening diameter of the skimmer 28, and the degree of vacuum in the third vacuum chamber 24 is
The pressure is maintained at about 10 ^-8 to 10 ^-7 Torr, which is indicated by the third vacuum gauge 13. Since the substrate 1 to be etched is arranged on the electrode 2 in the third vacuum chamber 24 so as to face the supersonic molecular flow J of the plasma flowing through the collimator 30, the supersonic molecular The flow J is blown perpendicular to the substrate 1 to be etched.

As described above, the substrate 1 to be etched has an extremely low gas temperature of several degrees or less in absolute temperature, that is, the thermal motion velocity of heavy particles such as neutral atomic molecules and ions is extremely small, and the interaction between heavy particles can be ignored. Since the supersonic molecular flow J of the reactive weakly ionized plasma is blown, ions and neutral atomic molecular radicals of the reactive weakly ionized plasma are vertically incident on the substrate surface as a low-temperature low-energy reactive particle beam. Therefore, the velocity component of ions and neutral atomic radicals in the horizontal direction with respect to the substrate surface becomes extremely small compared to the incident velocity in the vertical direction, and the incident energy is much smaller than the physical sputtering threshold. Become.

Here, for example, when a mixed gas of chlorine Cl ₂ and argon Ar is used as the etching gas A as in the conventional example, Cl is used as a neutral atomic radical, and Cl ⁺ and A are used as atomic ions.
r ⁺ , and Cl ₂ ⁺ as the molecular ion. In this case, there are no molecular radicals. Further, the gas density of the supersonic molecular flow of plasma, that is, the density of heavy particles such as neutral atomic molecules and ions is 10 ¹² to 10 ¹⁵ cm ^-3 , and the plasma density is 10
It is about ⁹ to 10 ¹² cm ^-3 .

FIG. 4 is a view for explaining a mechanism of etching a substance on a substrate disposed on an electrode facing the supersonic molecular flow of plasma in the dry etching apparatus using the supersonic molecular flow of plasma of this embodiment. It is a schematic diagram.
Also in this case, a space charge region (sheath) is formed near the substrate similarly to the conventional example, and the positive ions incident on the sheath region are accelerated in the direction of the substrate by a sheath potential (plasma potential) of about 10 V and are perpendicular to the substrate surface. Incident on.

On the other hand, the neutral radical does not respond to the sheath potential, but, unlike the conventional example, is incident perpendicularly to the substrate surface in a supersonic molecular flow state. Therefore, the chemical etching by the neutral radical which determines the selectivity of the etching becomes anisotropic and simultaneously gives the etching anisotropy.

In addition, the incident energy of ions on the substrate surface is still smaller than the physical sputtering threshold of about 20 eV even when accelerated by the sheath potential. No etching occurs due to the competition process with ions, and no damage occurs to the surface layer of the thin film to be etched.

After all, in the dry etching apparatus of this embodiment, the anisotropic chemical etching by neutral radicals controls the etching process of the substance on the substrate, and not only the super anisotropy but also the super high selectivity and the extremely low damage. Is also performed at the same time.

As described above, in the present embodiment, the plasma 10 generated by the discharge is supersonic expanded into the first vacuum chamber 22 through the nozzle 26 to form a supersonic free jet D of the plasma. The supersonic molecular flow E of plasma is extracted into the second vacuum chamber 23 through the skimmer 28, and the gas temperature is extremely low, that is, the thermal motion velocity of heavy particles such as neutral atomic molecules and ions is extremely small. Collimator for supersonic molecular flow of plasma with negligible interaction between
Since it is configured to blow the substrate 1 in the third vacuum chamber 24 through 30, plasma ions and neutral atomic molecules are vertically incident on the substrate surface as a low-temperature low-energy particle beam. In this case, the velocity component of ions and neutral radicals in the horizontal direction with respect to the substrate surface is extremely small as compared with the incident velocity in the vertical direction, and the incident energy is much smaller than the physical sputtering threshold. As a result, anisotropic chemical etching by neutral radicals controls the etching process of the substance on the substrate, and it is possible to realize not only ultra-high anisotropy but also ultra-high selectivity and ultra-low damage simultaneously. There is an effect that a dry etching apparatus using discharge plasma can be obtained.

In this embodiment, a continuous variable mechanism for the distance between the nozzle 26 and the skimmer 28 is provided as shown in FIG. 3, so that the supersonic free jet D of the plasma whose state changes in response to changes in various conditions is provided. The supersonic molecular flow E of the plasma can be optimally extracted.

In the above embodiment, the case where the incident energy of ions and neutral radicals is set to be smaller than the physical sputter threshold is described. Physical sputtering or the like may be performed supplementarily.

For example, depending on the type of the substance to be etched, the incident energy of ions on the substrate surface is set higher than the physical sputtering threshold, so that not only anisotropic chemical etching by neutral radicals but also physical sputtering by ions It is necessary to add etching by an ion assist process, which is a competition process between neutral radicals and ions. Therefore, in order to perform optimum etching in accordance with various substances to be etched, it is preferable to independently provide a means capable of increasing the incident energy of ions on the substrate surface.

Next, the case where such means for increasing the ion incident energy is provided will be described with reference to FIG.

Here, as shown in the drawing, an RF power applying means 43 for applying RF power to the electrode 2 on which the substrate 1 to be etched is mounted is provided, and a self-bias potential is generated in the electrode 2 to form the electrode 2 near the substrate. The sheath potential (plasma potential + electrode self-bias potential) of the sheath is increased. That is, when the RF power applied to the electrode 2 is increased by the RF power applying means 43, the sheath potential of the sheath formed near the substrate increases, and the acceleration of ions incident on the sheath region due to the sheath potential increases. Can increase the incident energy of ions to the substrate. This makes it possible to perform physical sputtering by ions and etching by an ion assist process.

Next, a second embodiment of the present invention will be described. FIG. 8 is a sectional view showing a main part of a dry etching apparatus according to a second embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts, and 34 is installed in the second vacuum chamber 23, and charged particles, from supersonic molecular flow E of plasma in the second vacuum chamber 23, That is, a pair of charged particle removing electrodes 35 for removing ions and electrons to form a supersonic molecular flow F of a neutral atomic molecular gas, and 35 is a DC voltage applying means for applying a voltage between the pair of electrodes 34. Thus, the electrode 34 and the DC voltage applying means 35 constitute a charged particle removing means. G is a supersonic molecular flow of the neutral atomic molecular gas which has flowed into the third vacuum chamber 24 after passing through the collimator 30 in the supersonic molecular flow F of the neutral atomic molecular gas, The substrate 1 to be etched is disposed on the electrode 2 in the third vacuum chamber 24 so as to face the supersonic molecular flow G.

 Next, the operation will be described.

The etching gas A is ionized in the discharge chamber 21, the ionized gas is supersonic expanded in the first vacuum chamber 22 to form a supersonic free jet D, and the supersonic free jet D is further separated from the jet D by the skimmer 28. The process up to the point where the flow E is extracted into the second vacuum chamber 23 is the same as that in the first embodiment, and a description thereof will be omitted.

In the second vacuum chamber 23, a pair of charged particle removing electrodes 34 is disposed so as to sandwich the supersonic molecular flow E of plasma, and a DC voltage applying means is provided between the pair of electrodes 34. 35
, And an electric field is generated in a direction perpendicular to the central axis of the supersonic molecular flow E. Therefore, the ions and electrons of the supersonic molecular flow E of the plasma flowing between the pair of electrodes 34 are separated and moved in opposite directions by an electric field perpendicular to the center axis of the flow of the supersonic molecular flow E. Is captured by the pair of electrodes 34. As a result, ions and electrons are removed from the supersonic molecular flow E of the plasma that has passed through the charged particle removing electrode 34, and a supersonic molecular flow F of a neutral atomic molecular gas is extracted.

In the supersonic molecular flow F of the neutral atomic molecular gas generated in this way, the gas temperature is extremely low at several degrees or less in absolute temperature as in the case of the supersonic molecular flow E of the plasma. The thermal velocity is extremely low and the interaction between particles is negligible. The supersonic molecular flow F of the neutral atomic molecular gas having such characteristics passes through the collimator 30 arranged on the second partition wall 29 and flows into the third vacuum chamber 24. Note here similar to the opening diameter of the collimator 30 in the first embodiment, or less opening diameter about the same skimmer 28 and the vacuum degree of the third vacuum chamber 24 is ^{10-8 - 7} Torr
Degree, which is indicated by the third vacuum gauge 13.

Then, in the third vacuum chamber 24, the supersonic molecular flow G of the neutral atomic molecular gas flowing through the collimator 30 flows.
Is vertically sprayed on the substrate 1 to be etched placed on the electrode 2.

As described above, the substrate 1 to be etched has a gas temperature extremely low as several degrees or less in absolute temperature, that is, a reactive neutral atom gas in which the thermal motion velocity of neutral atom molecules is extremely small and the interaction between particles can be ignored. Is sprayed, the neutral atomic radicals of the reactive neutral atomic gas are perpendicularly incident on the substrate surface as a low-temperature low-energy reactive particle beam. Therefore, the velocity component of the neutral atomic molecular radical in the horizontal direction with respect to the substrate surface is extremely small as compared with the incident velocity in the vertical direction, and the incident energy is much smaller than the physical sputtering threshold.

Next, the mechanism of etching of the supersonic molecular flow G of neutral atomic molecular gas and the substance on the substrate in the dry etching apparatus of the second embodiment will be described with reference to FIG.

In the apparatus of this embodiment, since the etching is performed by using a neutral atomic molecular gas instead of plasma, a space charge region (sheath) is not formed near the substrate, and there is no contribution to the etching of ions. On the other hand, the neutral atomic molecular radicals are perpendicularly incident on the substrate surface in the state of supersonic molecular flow, so the chemical etching of the substance on the substrate by the neutral radicals becomes anisotropic. Gives sex at the same time. Therefore, in the dry etching apparatus of this embodiment, the etching of the substance on the substrate proceeds only by the anisotropic chemical etching by the neutral radical, and the etching that simultaneously satisfies the ultra-high selectivity and the extremely low damage property is performed. .

Here, the supersonic molecular flow F of neutral atomic molecular gas generated by removing ions and electrons from the supersonic molecular flow E of plasma contains Cl as atomic radicals and has a gas density of 10 ¹² to 10 ¹⁵ cm. It is about ^-3 .

As described above, according to the present embodiment, the plasma 10 generated by the discharge is supersonic expanded through the nozzle 26 into the first vacuum chamber 22 to form a supersonic free jet D of the plasma, and then the supersonic free jet D is formed. From the sonic free jet D, a supersonic molecular flow E of plasma having a very low gas temperature and negligible interaction between heavy particles is extracted into the second vacuum chamber 23 through the skimmer 28, and the supersonic molecular flow E of this plasma is extracted. Ion and electrons are removed from the gas by the charged particle removing means, and the gas temperature is extremely low, that is, the thermal motion velocity of the neutral atomic molecule is extremely small, and the supersonic molecular flow F of the neutral atomic molecular gas in which the interaction between the particles can be ignored. And the supersonic molecular flow F of the neutral atom gas is blown onto the substrate 1 to be etched through the collimator 30. It will be perpendicularly incident on the substrate surface as over arm.

In this case, the velocity component of the neutral atomic molecular radical in the horizontal direction with respect to the substrate surface is extremely small as compared with the incident velocity in the vertical direction, and the incident energy is much smaller than the physical sputtering threshold. Therefore, the etching of the substance on the substrate proceeds only by the anisotropic chemical etching by the neutral atomic molecular radical, thereby achieving the etching satisfying not only the ultra-high anisotropy but also the ultra-high selectivity and the ultra-low damage simultaneously. There are effects that can be realized.

In addition, since the etching is performed by neutral atomic molecular radicals, there is an effect that electrostatic breakdown due to charge-up of the substrate to be etched can be prevented.

In the second embodiment, ions and electrons of the supersonic molecular stream E of plasma are removed by the charged particle removing electrode 34 installed in the second vacuum chamber 23, and the supersonic molecular stream of the neutral atomic molecule gas is removed. Although the case where the flow F is taken out has been described,
The charged particle removing electrode 34 may be provided in the third vacuum chamber 24. In this case, the supersonic molecular stream E of the plasma passes through the collimator 30 and flows into the third vacuum chamber 24, where ions and electrons are removed from the supersonic molecular stream of the plasma in the third vacuum chamber 24. The supersonic molecular flow of the neutral atomic molecular gas is taken out.

In the second embodiment, the case where only the electric field is used for the charged particle removing means has been described. However, both the electric field and the magnetic field may be used.

FIG. 10 is a cross-sectional configuration diagram for explaining a configuration using an electric field and a magnetic field. In this configuration, a pair of electrodes 34a having an opening at the center are installed to face the supersonic molecular flow E of plasma, DC voltage applying means 3 is provided between the pair of electrodes 34a.
A voltage is applied by 5 to generate an electric field parallel to the flow direction of the supersonic molecular flow E.

In this case, the ions and electrons of the supersonic molecular flow E of the plasma flowing between the pair of electrodes 34a are separated and moved in opposite directions by an electric field parallel to the central axis of the flow of the supersonic molecular flow. Of the electrode 34a. The charged particles that cannot be captured here are applied to a magnetic field applying means using a permanent magnet or an electromagnetic coil installed following the pair of electrodes 34a.
The direction is changed by 43a and removed from the supersonic molecular flow, and a supersonic molecular flow F of neutral atomic molecular gas is taken out. Here, the polarity of the DC voltage applying means 35 is negative, the direction of the magnetic field by the magnetic field applying means 43a is the γ direction perpendicular to the supersonic molecular flow, and I is the ion flow whose direction is changed by the magnetic field γ.

Further, in the first and second embodiments, the generation of the plasma in the reactive gas discharge chamber 21 is indirectly performed by a high-frequency induction glow discharge using RF or an arc discharge, that is, by a coil or the like mounted outside the discharge chamber. Although the case where the high-frequency current is induced inside is described, the plasma is generated by a high-frequency glow discharge or an arc discharge using RF or microwave, that is, for example,
In the case of RF discharge, a counter electrode may be arranged in the discharge chamber 21 so that high-frequency power is directly introduced into the discharge chamber to generate plasma, and an electron beam, an ion beam, a neutral particle, Plasma may be generated by ion irradiation discharge using a beam or a laser beam.

Further, in each of the above-described embodiments, the case where the mixed gas of chlorine and argon is used as the etching gas A to etch the polycrystalline silicon on the substrate 1 to be etched is described. However, another etching gas may be selected. Further, a substance to be etched other than polycrystalline silicon may be etched by selecting an appropriate etching gas.

Further, in each of the above embodiments, the case where the frequency of the RF power applying means 6 and 43 is 13.56 MHz has been described, but other frequencies may be used.

Furthermore, in the above embodiment, the opening diameter of the nozzle 26 is 1 m.
m, but the first evacuation means 3
The pumping speed of 1 is increased to make the opening diameter of the nozzle 26 larger than about 1 mm, and the pumping speed of the second vacuum pumping means 32 is further increased to adjust the opening diameter of the skimmer 28 to the opening diameter of the nozzle 26. May be larger.

In this case, in the apparatus of the first embodiment, the flux of the supersonic molecular flow E of the plasma extracted through the skimmer 28 is increased, and the pumping speed of the third vacuum pumping means 33 is increased to increase the diameter of the collimator 30. Is increased, the area to be etched on the substrate 1 to be etched and the etching rate are increased.

Further, in the apparatus of the second embodiment, the supersonic molecular flow F of the neutral atomic molecular gas extracted through the flux of the supersonic molecular flow E of the plasma extracted through the skimmer 28 and the charged particle removing electrode 34 is obtained. And the diameter of the collimator 30 is increased by increasing the pumping speed of the third vacuum pumping means 33, thereby increasing the area to be etched on the substrate 1 to be etched and the etching rate.

FIG. 11 is a sectional view showing a main part of a dry etching apparatus according to a third embodiment of the present invention. In the figure, 21 is a discharge chamber, 22 is a first vacuum chamber arranged adjacent to the discharge chamber 21, 23 is a second vacuum chamber arranged adjacent to the first vacuum chamber 22, 24 Is a third vacuum chamber having an electrode 2 on which the substrate to be etched 1 is mounted, and 26a is installed at one end 25 of the reactive gas discharge chamber 21. The opening cross section is a two-dimensional nozzle having a rectangular slit shape, 27 is a first partition partitioning the first vacuum chamber 22 and the second vacuum chamber 23, and 28a is installed in the first partition 27. A two-dimensional skimmer having an opening cross section of a rectangular slit shape; 29, a second partition separating the second vacuum chamber 23 and the third vacuum chamber 24; 30a, a second partition 29;
Is a collimator with a rectangular slit in cross section.

Reference numeral 31 denotes first vacuum exhaust means for exhausting the first vacuum chamber 22, and reference numerals 32, 33 denote the second and third vacuum chambers 23, 33, respectively.
The second and third vacuum exhaust means 24 for exhausting gas, 7 is a gas cylinder filled with the etching gas A to be supplied into the discharge chamber 21, and 8 is a gas cylinder filled with the etching gas from the gas cylinder 7 into the discharge chamber 21. Gas flow rate control means 9 for adjusting the flow rate is a pressure gauge for monitoring the gas pressure in the discharge chamber 21;
13 to 13 are first to third vacuum gauges for monitoring the degree of vacuum in the first to third vacuum chambers 22 to 24, respectively, 14 is a high-frequency induction coil installed around the discharge chamber 21; Reference numeral 6 denotes RF power applying means for applying RF power to the coil 14.

Reference numeral 10 denotes an RF induced discharge plasma generated in a portion of the discharge chamber 21 where the coil 14 is installed.
Is a supersonic free jet of plasma formed by supersonic expansion into the first vacuum chamber 22 through the nozzle 26a, and E is the second vacuum through the skimmer 28a from the supersonic free jet D of the plasma. The supersonic molecular flow J of the plasma extracted into the chamber 23 is a supersonic molecular flow of the plasma which has passed through the collimator 30a and flowed into the third vacuum chamber 24 among the supersonic molecular flow E of the plasma. The substrate to be etched 1 is a molecular flow, and the electrode 2 in the third vacuum chamber 24 is opposed to the supersonic molecular flow J of the plasma.
It is installed above.

The nozzle 26a, the skimmer 28a, and the collimator 30a each having a rectangular slit-shaped cross section are arranged on the same plane, and the supersonic free jet D in the first vacuum chamber 22 and the second vacuum chamber 23 Of the supersonic molecular flow E and the central plane of the supersonic molecular flow J in the third vacuum chamber 24.

Further, as a material to be etched, a base material, and a photoresist on the substrate 1 to be etched, for example, polycrystalline silicon, silicon oxide, and PMMA are used as in the conventional example, and the etching gas A filled in the gas cylinder 7 is also used. For example, a mixed gas of chlorine and argon is used as in the conventional example. The frequency of the RF power applying means 6 is 13.56 MHz, for example, as in the conventional example.

Next, the operation of the dry etching apparatus according to the above embodiment will be described.

First, the first to third vacuum chambers 22 to 24 are evacuated by the first to third vacuum exhaust means 31 to 33, respectively, and the reactive gas discharge chamber 21 and the first to third vacuum chambers 22 to 24 is set to a predetermined degree of vacuum.

Next, the etching gas A is introduced into the discharge chamber 21 from the gas cylinder 7 through the gas flow rate control means 8 while the first to third vacuum exhaust means 31 to 33 are evacuated. The gas pressure in the discharge chamber 21 is set by adjusting the etching gas flow rate by the gas flow rate control means 8 while monitoring the gas pressure.

Subsequently, the high frequency induction coil 14 is
When RF power is applied to the etching gas, the etching gas in the discharge chamber 21 is ionized by RF-induced glow discharge or arc discharge, and the reactive weakly ionized plasma 10 is generated. Here, the pressure in the discharge chamber 21 is about 10 ² to 10 ³ Torr, and the temperature is 10 ³ to 10 ⁴ Torr.
Degree, and the pressure is indicated by the pressure gauge 9.

The plasma of the etching gas A generated in the discharge chamber 21 is a two-dimensional nozzle 26 having a rectangular slit-shaped opening section.
After passing through a, it expands supersonically into the first vacuum chamber 22 to form a supersonic free jet D. The opening of the nozzle 26a is, for example,
The degree of vacuum is about 0.5 × 50 mm (aspect ratio 100) and the degree of vacuum in the first vacuum chamber 22 is maintained at about 10 ⁻³ to 10 ⁻² Torr, which is indicated by the first vacuum gauge 11. .

FIG. 12 shows the supersonic free jet D in detail. A supersonic free jet is characterized by a zone of supersonic free expansion flow called a Zone of Silence and a shock wave called a Barrel Shock and a Mach Disk surrounding the silence zone. Can be A jet boundary (Jet Boundary) is located around the barrel-shaped shock wave, and a reflected shock wave (Reflected Shoc) is located downstream of the Mach disk.
k) exists. In a supersonic free expansion flow in a quiet region, as the gas moves downstream along the center axis of the flow, the density and temperature of the plasma, that is, the plasma is formed by the supersonic free expansion of the gas, in other words, the adiabatic expansion of the gas. The density and temperature of neutral atomic molecules, ions, and electrons decrease. Therefore, the frequency of collision between plasma particles decreases and the degree of ionization freezes, but the flow velocity increases. Then, the gas temperature of the plasma, that is, the temperature of heavy particles such as neutral atomic molecules and ions is extremely low at several degrees or less in absolute temperature, about 10 times or more downstream of the short side of the opening of the nozzle 26a from the nozzle 26a, The collision frequency between heavy particles is almost infinite. However, the electron temperature of the plasma does not drop as much as the temperature of the heavy particles,
Stops about ^three times.

In such a supersonic free jet D of plasma, the supersonic free expansion is sufficiently developed along the flow direction, the gas temperature of the plasma is sufficiently reduced, and the thermal motion of heavy particles such as neutral atomic molecules and ions. The two-dimensional skimmer 28a having a rectangular slit-shaped cross section is disposed at a position where the velocity is extremely small and the interaction between the heavy particles can be ignored. Specifically, a skimmer 28a is installed on the first partition wall 27, and the opening of the skimmer 28a is
It has a shape that does not disturb upstream of the supersonic free jet D,
The short side of the opening is 2-3 of the short side of the opening of the nozzle 26a.
Approximately twice or less. A portion of the supersonic free jet D near the center axis in the quiet region of the supersonic free jet D formed in the first vacuum chamber 22 by the skimmer 28a is extracted as a supersonic molecular flow E in the second vacuum chamber 23. Is done. The degree of vacuum in the second vacuum chamber 23 is maintained at about 10 ⁻⁶ to 10 ⁻⁵ Torr, and this is displayed by the second vacuum gauge 12. The cross-sectional shape perpendicular to the flow of the supersonic molecular flow E is a rectangular slit shape.

By the way, the state of the supersonic free jet D of the plasma, for example, the change of the physical quantities such as the gas density, temperature, and flow velocity of the plasma along the size of the quiet region and the direction of the flow are as follows.
It is defined by various conditions such as the shape of the nozzle 26a and the size of the opening, the pressure in the discharge chamber 21, the degree of vacuum in the first vacuum chamber 22, and the like. Therefore, when extracting a supersonic molecular flow E of plasma from the quiet region of the supersonic free jet D of plasma formed in the first vacuum chamber 22 into the second vacuum chamber 23 through the skimmer 28a, the extraction is performed. It is preferable to provide a mechanism for continuously varying the distance between the nozzle 26a and the skimmer 28a in order to keep the distance optimally in response to changes in various conditions.

FIG. 13 shows an example of such a continuously variable mechanism of the distance between the nozzle 26a and the skimmer 28a. In the drawing, the discharge chamber 21 is connected to the first vacuum chamber 22 by, for example, a bellows 41, and the length of the bellows 41 is expanded and contracted to move the discharge chamber 21 in the directions of arrows α and β shown in FIG. Nozzle 26a−
The distance between the skimmers 28a can be continuously changed. Therefore, the supersonic molecular flow E of plasma can be optimally extracted from the supersonic free jet D of plasma whose state changes in response to changes in various conditions.

In the supersonic molecular flow E of the plasma extracted in the second vacuum chamber 23 in this manner, the gas temperature of the plasma is extremely low as a few degrees or less in absolute temperature, that is, heavy particles such as neutral atomic molecules and ions. Has a very small thermal velocity, and the interaction between heavy particles can be neglected. The supersonic molecular flow E of the plasma having such characteristics flows into the third vacuum chamber 24 through the collimator 30a having a rectangular slit cross section, which is provided on the second partition wall 29. Where the collimator 30
Is shorter than or equal to the short side of the opening of the skimmer 28a, and the degree of vacuum in the third vacuum chamber 24 is 10 ⁻⁸ to 10 ⁻⁷ To
rr, which is indicated by the third vacuum gauge 13. Since the substrate 1 to be etched is disposed on the electrode 2 so as to face the supersonic molecular flow J of the plasma flowing into the third vacuum chamber 24 through the collimator 30a, the supersonic molecular flow J is blown perpendicular to the substrate 1 to be etched. The supersonic molecular flow J
The cross section perpendicular to the flow is rectangular slit shape.

As described above, the substrate 1 to be etched has an extremely low gas temperature of several degrees or less in absolute temperature, that is, the thermal motion velocity of heavy particles such as neutral atomic molecules and ions is extremely small, and the interaction between heavy particles can be ignored. Since the supersonic molecular flow J of the reactive weakly ionized plasma is blown, ions and neutral atomic molecular radicals of the reactive weakly ionized plasma are vertically incident on the substrate surface as a low-temperature low-energy reactive particle beam. Therefore, the velocity component of ions and neutral atomic radicals in the horizontal direction with respect to the substrate surface becomes extremely small compared to the incident velocity in the vertical direction, and the incident energy is much smaller than the physical sputtering threshold. Become.

Here, for example, when a mixed gas of chlorine Cl ₂ and argon Ar is used as the etching gas A as in the conventional example, Cl is used as a neutral atomic radical, and Cl ⁺ and A are used as atomic ions.
r ⁺ , and Cl ₂ ⁺ as the molecular ion. In this case, there are no molecular radicals. Further, the gas density of the supersonic molecular flow of plasma, that is, the density of heavy particles such as neutral atomic molecules and ions is 10 ¹² to 10 ¹⁵ cm ^-3 , and the plasma density is 10
It is about ⁹ to 10 ¹² cm ^-3 .

FIG. 14 is a view for explaining a mechanism in which a substance on a substrate disposed on an electrode facing the supersonic molecular flow of plasma is etched in a dry etching apparatus using a supersonic molecular flow of plasma of this embodiment. It is a schematic diagram.
Also in this case, a space charge region (sheath) is formed near the substrate similarly to the conventional example, and the positive ions incident on the sheath region are accelerated in the direction of the substrate by a sheath potential (plasma potential) of about 10 V and are perpendicular to the substrate surface. Incident on.

On the other hand, the neutral radical does not respond to the sheath potential, but, unlike the conventional example, is incident perpendicularly to the substrate surface in a supersonic molecular flow state. Therefore, chemical etching using neutral radicals which determines the selectivity of etching becomes anisotropic, and anisotropy of etching can be obtained at the same time.

In addition, the incident energy of ions on the substrate surface is still smaller than the physical sputter threshold of about 20 eV even when accelerated by the sheath potential. No etching occurs due to a competition process with the thin film, and no damage occurs to the surface layer of the thin film to be etched.

After all, in the dry etching apparatus of this embodiment, the anisotropic chemical etching by neutral radicals controls the etching process of the substance on the substrate, and not only the super anisotropy but also the super high selectivity and the extremely low damage. Is also performed at the same time.

As described above, in the present embodiment, the plasma 10 generated by the discharge is supersonic expanded into the first vacuum chamber 22 through the nozzle 26a to form a supersonic free jet D of the plasma, and the supersonic free jet D A supersonic molecular flow E of plasma into the second vacuum chamber 23 through the skimmer 28a,
The supersonic molecular flow of the plasma, whose gas temperature is extremely low, that is, the thermal motion velocity of the heavy particles such as neutral atomic molecules and ions is extremely small and the interaction between the heavy particles is negligible, is passed through the collimator 30a to the third vacuum chamber 24. Since the plasma is sprayed on the substrate 1 to be etched, the plasma ions and neutral atom molecules are vertically incident on the substrate surface as a low-temperature low-energy particle beam. In this case, the velocity component of ions and neutral radicals in the horizontal direction with respect to the substrate surface is extremely small as compared with the incident velocity in the vertical direction, and the incident energy is much smaller than the physical sputtering threshold. As a result, anisotropic chemical etching by neutral radicals controls the etching process of the substance on the substrate, and it is possible to realize not only ultra-high anisotropy but also ultra-high selectivity and ultra-low damage simultaneously. There is an effect that a dry etching apparatus using discharge plasma can be obtained.

In the present embodiment, as shown in FIG.
Since a continuous variable mechanism of the distance between the skimmers 28a is provided,
The supersonic molecular flow E of plasma can be optimally extracted from the supersonic free jet D of plasma whose state changes in response to changes in various conditions.

In the above embodiment, the case where the incident energy of ions and neutral radicals is set to be smaller than the physical sputter threshold is described. Physical sputtering may be performed in an auxiliary manner.

For example, depending on the type of the substance to be etched, the incident energy of ions on the substrate surface is set higher than the physical sputtering threshold, so that not only anisotropic chemical etching by neutral radicals but also physical sputtering by ions It is necessary to add etching by an ion assist process, which is a competition process between neutral radicals and ions. Therefore, in order to perform optimum etching in accordance with various substances to be etched, it is preferable to independently provide a means capable of increasing the incident energy of ions on the substrate surface.

FIG. 15 shows a case where such means for increasing the ion incident energy is provided.

Here, the electrode 2 on which the substrate 1 to be etched is
An RF electrode applying means 43 for applying RF power is provided to generate a self-bias potential on the electrode 2, thereby increasing the sheath potential (plasma potential + electrode self-bias potential) of the sheath formed near the substrate. That is, when the RF power applied to the electrode 2 is increased by the RF power applying means 43, the sheath potential of the sheath formed near the substrate increases, and the acceleration of ions incident on the sheath region due to the sheath potential increases. Can increase the incident energy of ions to the substrate. As a result, not only anisotropic chemical etching by neutral radicals but also physical sputtering by ions and etching by an ion assist process, which is a competitive process between neutral radicals and ions, proceed.

Next, a fourth embodiment of the present invention will be described. FIG. 16 is a sectional view of a principal part showing the configuration of a dry etching apparatus according to a fourth embodiment of the present invention. 11, the same reference numerals as those in FIG. 11 denote the same or corresponding parts, and 34 is installed in the second vacuum chamber 23, and charged particles, from supersonic molecular flow E of plasma in the second vacuum chamber 23, That is, a pair of charged particle removing electrodes 35 for removing ions and electrons to form a supersonic molecular flow F of a neutral atomic molecular gas, and 35 is a DC voltage applying means for applying a voltage between the pair of electrodes 34. The electrode 34 and the DC voltage applying means 35 constitute a charged particle removing means. G is a supersonic molecular flow of the neutral atomic molecular gas in the supersonic molecular flow F of the neutral atomic molecular gas that has passed through the collimator 30a and flowed into the third vacuum chamber 24. The substrate 1 to be etched has the supersonic molecular flow G
The electrode is disposed on the electrode 2 in the third vacuum chamber 24 so as to face the electrode.

 Next, the operation will be described.

The etching gas A is ionized in the discharge chamber 21, and the ionized gas is supplied to the two-dimensional nozzle 26a having a rectangular slit-shaped opening section.
Through the supersonic free jet D in the first vacuum chamber 22 to form a supersonic free jet D. Further, the opening cross section is perpendicular to the flow from the supersonic free jet D by a two-dimensional skimmer 28a having a rectangular slit shape. The process up to the point where the supersonic molecular flow E of the plasma having a rectangular cross section is extracted into the second vacuum chamber 23 is the same as that in the third embodiment, and the description thereof is omitted.

In the second vacuum chamber 23, a pair of charged particle removing electrodes 34 is disposed so as to sandwich the supersonic molecular flow E of plasma, and a DC voltage applying means is provided between the pair of electrodes 34. 35
, And an electric field is generated in a direction perpendicular to the flow direction of the supersonic molecular flow E. Accordingly, the ions and electrons of the supersonic molecular flow E of the plasma flowing between the pair of electrodes 34 are separated and moved in directions opposite to each other by an electric field perpendicular to the direction of the flow of the supersonic molecular flow E. It is captured by the pair of electrodes 34. As a result, the charged particle removing electrode 34
The ions and electrons are removed from the supersonic molecular flow E of the plasma that has passed, and a supersonic molecular flow F of a neutral atomic molecular gas is extracted. Here, the cross-sectional shape perpendicular to the flow of the supersonic molecular flow F is also a rectangular slit shape.

In the supersonic molecular flow F of the neutral atomic molecular gas generated in this way, the gas temperature is extremely low at several degrees or less in absolute temperature as in the case of the supersonic molecular flow E of the plasma. The thermal velocity is extremely low and the interaction between particles is negligible. The supersonic molecular flow F of the neutral atomic molecule gas having such characteristics passes through the collimator 30a having a rectangular slit shape in section disposed on the second partition wall 29 and flows into the third vacuum chamber 24. I do. Here, the short side of the opening of the collimator 30a is the same as in the third embodiment.
It is less than or equal to the short side of the opening of the skimmer 28a, and the degree of vacuum in the third vacuum chamber 24 is maintained at about 10 ^-8 to 10 ^-7 Torr, which is indicated by the third vacuum gauge 13. ing.

In the third vacuum chamber 24, the collimator 30a
Supersonic molecular flow G of neutral atomic molecular gas flowing through
Is vertically sprayed on the substrate 1 to be etched placed on the electrode 2. The cross-sectional shape perpendicular to the flow of the supersonic molecular flow G is a rectangular slit shape.

As described above, the substrate 1 to be etched has a gas temperature extremely low as several degrees or less in absolute temperature, that is, a reactive neutral atom gas in which the thermal motion velocity of neutral atom molecules is extremely small and the interaction between particles can be ignored. Is sprayed, the neutral atomic radicals of the reactive neutral atomic gas are perpendicularly incident on the substrate surface as a low-temperature low-energy reactive particle beam. Accordingly, the velocity component of the neutral atomic molecular radical in the horizontal direction on the substrate surface is extremely small as compared with the incident velocity in the vertical direction, and the incident energy is much smaller than the physical sputtering threshold.

FIG. 17 is a schematic diagram for explaining a mechanism of etching a substance on a substrate disposed opposite to a supersonic molecular flow of a neutral atomic molecular gas in the dry etching apparatus of the fourth embodiment. is there. In the apparatus of this embodiment, since etching is performed using a neutral atomic molecule gas instead of plasma, a space charge region (sheath) is not formed near the substrate, and there is no contribution to ion etching. On the other hand, the neutral atomic molecular radicals are perpendicularly incident on the substrate surface in the state of supersonic molecular flow, so the chemical etching of the substance on the substrate by the neutral radicals becomes anisotropic. Gives sex at the same time. Therefore, in the dry etching apparatus of this embodiment, the etching of the substance on the substrate proceeds only by anisotropic chemical etching using neutral radicals, and not only ultra-high anisotropy but also ultra-high selectivity and ultra-low damage property are obtained. At the same time, satisfactory etching is performed.

Here, the supersonic molecular flow F of neutral atomic molecular gas generated by removing ions and electrons from the supersonic molecular flow E of plasma contains Cl as atomic radicals and has a gas density of 10 ¹² to 10 ¹⁵ cm. It is about ^-3 .

As described above, according to the present embodiment, the plasma 10 generated by the discharge is supersonic-expanded into the first vacuum chamber 22 through the nozzle 26a to form a supersonic free jet D of the plasma. A supersonic molecular flow E of plasma having extremely low gas temperature and negligible interaction between heavy particles is extracted from the free jet D through the skimmer 28a into the second vacuum chamber 23, and further, from the supersonic molecular flow E of this plasma. The ions and electrons are removed by the charged particle removing means, and the gas temperature is extremely low, that is, the supersonic molecular flow F of the neutral atomic molecule gas, in which the thermal motion velocity of the neutral atomic molecules is extremely small and the interaction between the particles can be ignored. Since the structure is such that the substrate is blown onto the substrate 1 through the collimator 30a, the neutral atomic molecules are vertically incident on the substrate surface as a low-temperature low-energy particle beam.

In this case, the velocity component of the neutral atomic molecular radical in the horizontal direction with respect to the substrate surface is extremely small as compared with the incident velocity in the vertical direction, and the incident energy is much smaller than the physical sputtering threshold. Therefore, the etching of the substance on the substrate proceeds only by the anisotropic chemical etching by the neutral atomic molecular radical, thereby achieving the etching satisfying not only the ultra-high anisotropy but also the ultra-high selectivity and the ultra-low damage simultaneously. There are effects that can be realized.

In addition, since the etching is performed by neutral atomic molecular radicals, there is also an effect that electrostatic destruction due to charging (charge-up) of the substrate to be etched by charged particles can be prevented.

In the fourth embodiment, ions and electrons of the supersonic molecular stream E of plasma are removed by the charged particle removing electrode 34 installed in the second vacuum chamber 23, and the supersonic molecular stream of neutral atomic molecular gas is removed. Although the case where the flow F is taken out has been described,
The charged particle removing electrode 34 may be provided in the third vacuum chamber 24. In that case, the supersonic molecular flow E of the plasma is a collimator
After passing through 30a and flowing into the third vacuum chamber 24, removing ions and electrons from the supersonic molecular flow of the plasma in the third vacuum chamber 24 and extracting the supersonic molecular flow of the neutral atomic molecular gas become.

In the fourth embodiment, the case where only the electric field is used for the charged particle removing means has been described. However, both the electric field and the magnetic field may be used.

FIG. 18 is a cross-sectional configuration diagram for explaining a configuration using an electric field and a magnetic field. In this configuration, a pair of electrodes 34a having a rectangular opening at the center face the supersonic molecular flow E of plasma. A voltage is applied between the pair of electrodes 34a by the DC voltage applying means 35, and an electric field is generated in parallel with the flow direction of the supersonic molecular flow E.

In this case, the ions and electrons of the supersonic molecular flow E of the plasma flowing between the pair of electrodes 34a are separated in opposite directions by an electric field parallel to the flow direction of the supersonic molecular flow.
The supersonic molecular flow is moved and further removed from the supersonic molecular flow by the magnetic field applying means 43a using a permanent magnet or an electromagnetic coil installed following the pair of electrodes 34a, and the supersonic molecular flow F is taken out. Here, the polarity of the DC voltage applying means 35 is negative, and the magnetic field applying means 43a is
The direction of the magnetic field due to is the γ direction perpendicular to the direction of the flow of the supersonic molecular flow, and I is the ion flow turned by the magnetic field γ.

Further, a fifth embodiment of the present invention will be described. 19th
FIG. 5 is a partial sectional view showing the vicinity of a substrate 1 to be etched in a dry etching apparatus according to a fifth embodiment of the present invention. 11, the same reference numerals as those in FIGS. 11 and 16 denote the same or corresponding parts, and 50 denotes a position of the substrate 1 to be etched, and a supersonic molecular flow J of plasma or a supersonic molecule of a neutral atomic molecular gas during etching. The direction of movement relative to the flow G is shown.

Next, the operation will be described. In the third and fourth embodiments of the present invention, the plasma generated in the discharge chamber 21 is supersonic-expanded into the first vacuum chamber 22 through the two-dimensional nozzle 26a having a rectangular slit-shaped cross section. A supersonic free jet D of the plasma is formed, and a supersonic molecular flow E of the plasma is extracted from the supersonic free jet D into the second vacuum chamber 23 through a two-dimensional skimmer 28a having a rectangular slit-shaped opening section. Therefore, the supersonic molecular flow E is a sheet-like beam having a rectangular slit shape in cross section perpendicular to the flow. Accordingly, subsequently, the supersonic molecular flow J of the plasma that has flowed into the third vacuum chamber 24 after passing through the collimator 30a having a rectangular slit cross section, or passing through the charged particle removing electrode 34 and the collimator 30a. The supersonic molecular flow G of the neutral atomic molecular gas flowing into the third vacuum chamber 24 has a rectangular slit-shaped cross section perpendicular to the flow. Therefore, when etching, the position of the substrate 1 to be etched is moved in the short side direction 50, so that etching that simultaneously satisfies ultra-high anisotropy, ultra-high selectivity, and ultra-low damage can be performed on a substrate having a larger diameter. There is a possible effect. here,
The diameter of the substrate 1 to be etched is about the long side of the cross section perpendicular to the flow of the supersonic molecular flow J of the plasma, which is a sheet beam, or the supersonic molecular flow G of a neutral atomic gas, and thus the cross section is rectangular. Slit-shaped two-dimensional nozzle
The length is about the long side of the opening of the 26a and the two-dimensional skimmer 28a.

In the third, fourth, and fifth embodiments, the generation of the plasma in the discharge test chamber 21 is performed by a high-frequency induction glow discharge using RF or an arc discharge, that is, the coil 14 installed outside the discharge chamber. Although the case where the high-frequency electric field is indirectly induced in the inside by the method described above is explained, this is the case where the plasma is generated.
RF or microwave high-frequency glow discharge or arc discharge is used. That is, a counter electrode or an antenna is arranged in the discharge chamber 21, thereby generating a high-frequency electric field directly in the discharge chamber to generate plasma. Or microwave, electron beam,
The plasma may be generated by beam irradiation ionization discharge using an ion beam, a neutral particle beam, a laser beam, or the like.

Further, in each of the above-described embodiments, the case where the mixed gas of chlorine and argon is used as the etching gas A to etch the polycrystalline silicon on the substrate 1 to be etched is described. However, another etching gas may be selected. Further, a substance to be etched other than polycrystalline silicon may be etched by selecting an appropriate etching gas.

Further, in each of the above embodiments, the case where the frequency of the RF applying means 6 and 43 is 13.56 MHz has been described, but other frequencies may be used.

Furthermore, in each of the above embodiments, the opening of the two-dimensional nozzle 26a having a rectangular slit in cross section is 0.5 × 50 mm (aspect ratio: 100).
Although the case of the degree has been described, the first evacuation means 31
To increase the opening area of the nozzle 26a, and further increase the exhaust rate of the second vacuum evacuation means 32 to increase the opening area of the two-dimensional skimmer 28a having a rectangular slit cross section. May be increased in accordance with the area of the opening.

In this case, in the apparatus of the third embodiment, the flux of the supersonic molecular stream E of the plasma extracted through the skimmer 28a increases, and the pumping speed of the third vacuum pumping means 33 is increased to increase the opening of the collimator 30a. Is increased, the area to be etched on the substrate 1 to be etched and the etching rate are increased.

Further, in the apparatus of the fourth embodiment, the supersonic molecular flow E of the neutral atomic molecular gas which is extracted through the flux of the supersonic molecular flow E of the plasma extracted through the skimmer 28a and the charged particle removing electrode 34 is obtained. Is increased, the pumping speed of the third vacuum pumping means 33 is increased, and the opening of the collimator 30a is increased, so that the area to be etched and the etching rate on the substrate 1 to be etched are increased.

Further, in the fifth embodiment, it is particularly effective to increase the aspect ratio of the openings of the two-dimensional nozzle 26a and the two-dimensional skimmer 28a whose cross section is a rectangular slit. The longer side of the opening is made longer, and the position of the substrate 1 to be etched moves in the direction of the shorter side relative to the supersonic molecular flow J or G whose cross section perpendicular to the flow has a rectangular slit shape. By performing the etching while performing the etching, the etching of a substrate having a larger diameter becomes possible.

FIG. 20 is a cross-sectional view of a principal part showing a configuration of a dry etching apparatus according to a sixth embodiment of the present invention. In the figure, 21 is a discharge chamber, 22 is a first vacuum chamber arranged adjacent to the discharge chamber 21, 23 is a second vacuum chamber arranged adjacent to the first vacuum chamber 22, 24 Is a third vacuum chamber which is arranged adjacent to the second vacuum chamber 23 and has the electrode 2 for mounting the substrate 1 to be etched, 26 is a nozzle installed at one end 25 of the discharge chamber 21, Reference numeral 27 denotes a first partition partitioning the first vacuum chamber 22 and the second vacuum chamber 23, and 28 denotes the first partition.
A skimmer installed on the partition wall 27 of the second vacuum chamber
A second partition 30 that partitions the 23 from the third vacuum chamber 24 is a collimator installed on the second partition 29.

Reference numeral 31 denotes first vacuum exhaust means for exhausting the first vacuum chamber 22, and reference numerals 32, 33 denote the second and third vacuum chambers 23, 33, respectively.
24, a second and third vacuum exhaust means for exhausting gas, 7 is a first gas cylinder filled with an etching gas A to be supplied into the discharge chamber 21, and 8 is a first gas cylinder from the first gas cylinder 7 to the discharge chamber 21. First gas flow rate control means for adjusting the flow rate of the etching gas into the inside, 15 is a second gas cylinder filled with light element gas B to be supplied into the discharge chamber 21, and 16 is the second gas cylinder 15 Second gas flow control means for adjusting the flow rate of the light element gas into the discharge chamber 21, 9 is a pressure gauge for monitoring the gas pressure in the discharge chamber 21, and 11 to 13 are the first to 3, a first to third vacuum gauges for monitoring the degree of vacuum in the vacuum chambers 22 to 24, 14 is a high-frequency induction coil installed around the discharge chamber 21, and 6 is an RF power supply for the coil 14. This is a means for applying RF power.

Reference numeral 10 denotes an RF induced discharge plasma generated in a portion of the discharge chamber 21 where the coil 14 is installed.
Is a supersonic free jet of plasma formed by supersonic expansion into the first vacuum chamber 22 through the nozzle 26, and E is a supersonic free jet of the plasma from the supersonic free jet D through the skimmer 28 to the second vacuum. The supersonic molecular flow J of the plasma extracted into the chamber 23 is the supersonic molecular flow E of the plasma that has passed through the collimator 30 and flowed into the third vacuum chamber 24 among the supersonic molecular flow E of this plasma. Molecular flow,
The substrate 1 to be etched is placed on the electrode 2 in the third vacuum chamber 24 so as to face the supersonic molecular flow J of the plasma.

The nozzle 26, the skimmer 28, and the collimator 30 are arranged in a straight line, and the supersonic free jet D in the first vacuum chamber 22, the supersonic molecular flow E in the second vacuum chamber 23, And on the same axis as the central axis of the supersonic molecular flow J in the third vacuum chamber 24.

Further, as a material to be etched, a base material, and a photoresist on the substrate 1 to be etched, for example, polycrystalline silicon, silicon oxide, and PMMA are used as in the conventional example, and an etching gas filled in the first gas cylinder 7 is used. As A, for example, chlorine is used as in the conventional example.
The frequency of the RF power applying means 6 is 13.56 MHz, for example, as in the conventional example.

Further, as the light element gas B filled in the second gas cylinder 15, for example, helium He is used.

Next, the operation of the dry etching apparatus according to the above embodiment will be described.

First, the first to third vacuum chambers 22 to 24 are evacuated by the first to third vacuum exhaust means 31 to 33, respectively, and the discharge chamber 21 is evacuated.
And the first to third vacuum chambers 22 to 24 are set to a predetermined degree of vacuum. Next, the etching gas A is introduced from the first gas cylinder 7 into the discharge chamber 21 through the first gas flow rate control means 8 while the first to third vacuum exhaust means 31 to 33 are evacuated. From the gas cylinder 15 to the second gas flow control means 16
Through which the light element gas B is introduced. And pressure gauge 9
The gas pressure in the discharge chamber 21 is monitored by monitoring the gas pressure in the discharge chamber 21 by the first gas flow rate control means 8 and the light element gas flow rate by the second gas flow rate control means 16. Set gas pressure.

Subsequently, the high frequency induction coil 14 is
When RF power is applied to the mixture, the mixed gas of the etching gas and the light element gas in the discharge chamber 21 is ionized by RF-induced glow discharge or arc discharge, and the reactive weakly ionized plasma 10 is generated. Here, the pressure in the discharge chamber 21 is about 10 ² to 10 ³ Torr, and the temperature is about 10 ³ to 10 ⁴ degrees, which is indicated by the pressure gauge 9.

The plasma of the mixed gas of the etching gas A and the light element gas B generated in the discharge chamber 21 passes through the nozzle 26 and expands supersonically into the first vacuum chamber 22 to form a supersonic free jet D. The opening diameter of the nozzle 26 is, for example, about 1 mm, and the degree of vacuum in the first vacuum chamber 22 is maintained at about 10 ^-3 to 10 ^-2 Torr, which is indicated by the first vacuum gauge 11. You.

FIG. 21 shows details of the supersonic free jet D. The supersonic free jet is a zone of supersonic free expansion flow called a zone of silence, a barrel-shaped shock wave (Barrel Shock) and a Mach disk (Mach Disk) surrounding the zone of silence.
It is characterized by a shock wave called. A jet boundary (Jet Boundary) surrounds the barrel-shaped shock wave.
The reflected shock wave (Reflected Shoc) is located downstream of the Mach disk.
k) exists. In a supersonic free-expansion flow in a quiet region, the density and temperature of the plasma, i.e., the density of the plasma due to the supersonic free expansion of the gas, in other words, the adiabatic expansion of the gas, as it moves downstream along the flow direction. The density and temperature of neutral molecules, ions, and electrons decrease.
Therefore, the frequency of collision between plasma particles decreases and the degree of ionization freezes, but the flow velocity increases. Further, the gas temperature of the plasma, that is, the temperature of heavy particles such as neutral atomic molecules and ions is extremely low at several degrees or less in absolute temperature, and the temperature of heavy particles is about 10 times or more downstream of the opening diameter of the nozzle 26 from the nozzle 26. The collision frequency between them is almost infinitesimal. However, the electron temperature of the plasma as the temperature of the heavy particles without lowering is stopped about 10 ³ times.

FIG. 22 shows details of the flow characteristics in the quiet region of the supersonic free jet D for a monoatomic molecular gas. In the flow of supersonic free expansion from the discharge chamber 21 in which the temperature of the gas is maintained at T ₀ through the nozzle 26 into the first vacuum chamber 22, as the gas moves downstream along its central axis, the gas Temperature T
Decreases while the velocity u of the flow increases. in this case,
Considering the conservation of enthalpy of the flow, the upper limit of the value of the kinetic energy 1 / 2Mu ^{2 for} the velocity u is 1/21 / 25kT ₀ ,
Therefore, the upper limit of the value of the speed u is (5 kT ₀ / M) ^1/2 . Here, M is the mass of the atom, and k is the Boltzmann constant. When the light element gas helium He is compared with, for example, argon Ar, when the temperature T ₀ is the same, the upper limit speed of He (5 kT ₀ / M _He ) ^1/2 is Ar
3 times faster than the upper limit speed (5kT ₀ / M _Ar ) ^1/2 .
Considering a mixed gas of a reactive gas and He or Ar, if the mixing ratio of the reactive gas and the He or Ar gas is set to about 5% or less, the reactive gas in the quiet region of the supersonic free jet D is formed. The flow velocity for atomic molecules is He or Ar
About the speed of flow.

Therefore, when the reactive gas is mixed with the light element gas He and subjected to supersonic free expansion, compared with the case where the reactive gas is mixed with Ar,
A value about three times faster for the flow velocity for the reactive gas atom molecules can be obtained.

In such a supersonic free jet D of plasma, the supersonic free expansion is sufficiently developed along the central axis of the flow, the gas temperature of the plasma is sufficiently reduced, and the heat of heavy particles such as neutral atomic molecules and ions is generated. The skimmer 28 is arranged at a position where the movement speed is extremely small and the interaction between the heavy particles can be ignored. Specifically, a skimmer 28 is installed on the first partition wall 27, and the opening of the skimmer 28 has a shape that does not disturb the upstream of the supersonic free jet D, and the opening diameter is the opening diameter of the nozzle 26. Of 2
Approximately three times or less. A portion of the supersonic free jet D formed by the skimmer 28 in the quiet region of the supersonic free jet D near the central axis is extracted as a supersonic molecular flow E into the second vacuum chamber 23. Is done. The degree of vacuum in the second vacuum chamber 23 is maintained at about 10 ⁻⁶ to 10 ⁻⁵ Torr, and this is displayed by the second vacuum gauge 12.

By the way, the state of the supersonic free jet D of the plasma, for example, changes in physical quantities such as the size of the quiet region and the plasma gas density, temperature, and flow velocity along the central axis of the flow depend on the shape of the nozzle 26 and It is defined by various conditions such as the opening diameter, the pressure in the discharge chamber 21 and the degree of vacuum in the first vacuum chamber 22. Therefore, when extracting the supersonic molecular flow E of plasma from the quiet region of the supersonic free jet D of plasma formed in the first vacuum chamber 22 into the second vacuum chamber 23 through the skimmer 28, the extraction is performed. In order to keep optimally in response to changes in various conditions, it is preferable to provide a mechanism for continuously varying the distance between the nozzle 26 and the skimmer 28.

FIG. 23 shows an example of such a continuously variable mechanism of the distance between the nozzle 26 and the skimmer 28. In the figure, the discharge chamber 21 is connected to the first vacuum chamber 22 by, for example, a bellows 41, and the length of the bellows 41 is expanded and contracted to move the discharge chamber 21 in the directions of arrows α and β shown in FIG. The distance between the nozzle 26 and the skimmer 28 can be changed continuously. Therefore,
The supersonic molecular flow E of plasma can be optimally extracted from the supersonic free jet D of plasma whose state changes in response to changes in various conditions.

In the supersonic molecular flow E of the plasma extracted in the second vacuum chamber 23 in this manner, the gas temperature of the plasma is extremely low as a few degrees or less in absolute temperature, that is, heavy particles such as neutral atomic molecules and ions. Has a very small thermal velocity, and the interaction between heavy particles can be neglected. The supersonic molecular flow E of the plasma having such characteristics passes through the cometer 30 provided on the second partition wall 29 and flows into the third vacuum chamber 24. Here, the opening diameter of the collimator 30 is equal to or less than the opening diameter of the skimmer 28, and the degree of vacuum in the third vacuum chamber 24 is
The pressure is maintained at about 10 ^-8 to 10 ^-7 Torr, which is indicated by the third vacuum gauge 13. Since the substrate 1 to be etched is disposed on the electrode 2 so as to face the supersonic molecular flow J of the plasma flowing into the third vacuum chamber 24 through the collimator 30, the supersonic molecular flow of the plasma J is to be blown perpendicular to the substrate 1 to be etched.

As described above, the substrate 1 to be etched has an extremely low gas temperature of several degrees or less in absolute temperature, that is, the thermal motion velocity of heavy particles such as neutral atomic molecules and ions is extremely small, and the interaction between heavy particles can be ignored. Since the supersonic molecular flow J of the reactive weakly ionized plasma is blown, ions and neutral atomic molecular radicals of the reactive weakly ionized plasma are vertically incident on the substrate surface as a low-temperature low-energy reactive particle beam. Therefore, the velocity components of ions and neutral radicals in the horizontal direction with respect to the substrate surface are extremely small compared to the incident velocity in the vertical direction, and the incident energy is much smaller than the physical sputter threshold. .

Here, when, for example, chlorine Cl ₂ is used as the etching gas A as in the conventional example, and helium He is used as the light element gas B, Cl is used as a neutral atomic radical, Cl ⁺ and He ⁺ are used as atomic ions, and Cl ₂ ⁺ is generated as a molecular ion. In this case, there are no molecular radicals. In addition, the gas density of the supersonic molecular flow of plasma, that is, the density of heavy particles such as neutral atomic molecules and ions is 10 ¹² to 10 ¹⁵ cm ^-3 ,
The plasma density is on the order of 10 ⁹ -10 ¹² cm ^-3 . Here, when the gas temperature of the discharge chamber 22 is T ₀ = 10 ⁴ K and the mixing ratio of chlorine gas and helium gas is about 5% or less, the upper limit of the velocity in the flow direction of the supersonic molecular flow is (5 kT ₀ / M _He ) ^1/2 1/21 × 10 ⁶ cm / sec
And the kinetic energies for He and Cl are each 2e
V, equivalent to about 19 eV.

FIG. 24 is a view for explaining a mechanism in which a substance on a substrate disposed on an electrode facing the supersonic molecular flow of plasma is etched in a dry etching apparatus using a supersonic molecular flow of plasma of this embodiment. It is a schematic diagram.
Also in this case, a space charge region (sheath) is formed near the substrate similarly to the conventional example, and the positive ions incident on the sheath region are accelerated in the direction of the substrate by a sheath potential (plasma potential) of about 10 V and are perpendicular to the substrate surface. Incident on.

On the other hand, the neutral radical does not respond to the sheath potential, but, unlike the conventional example, is incident perpendicularly to the substrate surface in a supersonic molecular flow state. Therefore, chemical etching using neutral radicals which determines the selectivity of etching becomes anisotropic, and anisotropy of etching can be obtained at the same time.

In addition, the incident energy of ions on the substrate surface is still smaller than the physical sputter threshold of about 20 eV even when accelerated by the sheath potential. No etching occurs due to a competition process with the thin film, and no damage occurs to the surface layer of the thin film to be etched.

After all, in the dry etching apparatus of this embodiment, the anisotropic chemical etching due to the neutral radicals incident on the substrate surface at a high speed governs the etching process of the substance on the substrate. Etching that simultaneously satisfies both high selectivity and extremely low damageability is performed.

As described above, in the present embodiment, the plasma of the mixed gas of the etching gas A and the light element gas B generated by the discharge is used.
The supersonic free expansion jet 10 of the plasma is formed by supersonic expansion of the nozzle 10 into the first vacuum chamber 22 through the nozzle 26, and the supersonic free jet D is further passed through the skimmer 28 to the second vacuum chamber.
The supersonic molecular flow E of the plasma is extracted into 23, and the gas temperature is extremely low, that is, the thermal motion velocity of the heavy particles such as neutral atomic molecules and ions is extremely small, and the interaction between the heavy particles can be ignored. Since the supersonic molecular flow is blown to the substrate 1 to be etched in the third vacuum chamber 24 through the collimator 30, the plasma ions and neutral atomic molecules are perpendicular to the substrate surface as a low-temperature low-energy particle beam. Will be incident. In this case, the velocity component of ions and neutral radicals in the horizontal direction with respect to the substrate surface is extremely small as compared with the incident velocity in the vertical direction, and the incident energy is much smaller than the physical sputtering threshold. Also, when the mixing ratio of the reactive gas to the light element gas is reduced, the incident velocity of ions and neutral radicals on the reactive gas in the direction perpendicular to the substrate surface is almost equal to the incident velocity of atomic molecules on the light element gas. Up to the value.
As a result, more anisotropic chemical etching due to fast neutral radicals governs the etching process of the substance on the substrate,
There is an effect that a dry etching apparatus using discharge plasma capable of realizing high-speed etching satisfying not only ultra-high anisotropy but also ultra-high selectivity and ultra-low damage can be obtained.

Further, in the present embodiment, as shown in FIG. 23, a continuous variable mechanism of the distance between the nozzle 26 and the skimmer 28 is provided, so that the supersonic free jet D of the plasma whose state changes in response to changes in various conditions is provided. The supersonic molecular flow E of the plasma can be optimally extracted.

In the above embodiment, the case where the incident energy of ions and neutral radicals is set to be smaller than the physical sputter threshold is described. Physical sputtering may be performed in an auxiliary manner.

For example, depending on the type of the substance to be etched, the incident energy of ions on the substrate surface is set higher than the physical sputtering threshold, so that not only anisotropic chemical etching by neutral radicals but also physical sputtering by ions It is necessary to add etching by an ion assist process, which is a competition process between neutral radicals and ions. Therefore, in order to perform optimum etching in accordance with various substances to be etched, it is preferable to independently provide a means capable of increasing the incident energy of ions on the substrate surface.

FIG. 25 shows a case where such means for increasing the ion incident energy is provided. Here, an RF power applying means 43 for applying an RF power to the electrode 2 on which the substrate 1 to be etched is mounted is provided, and a self-bias potential is generated at the electrode 2 so that a sheath potential of a sheath formed near the substrate is generated. (Plasma potential + electrode self-bias potential). That is, when the RF power is increased, the sheath potential of the sheath formed near the substrate increases, and the acceleration due to the sheath potential of ions incident on the sheath region increases,
The incident energy of ions on the substrate surface can be increased. As a result, not only anisotropic chemical etching by neutral radicals but also physical sputtering by ions and etching by an ion assist process, which is a competitive process between neutral radicals and ions, proceed.

 Next, a seventh embodiment of the present invention will be described.

FIG. 26 is a sectional view showing a main part of a dry etching apparatus according to a seventh embodiment of the present invention. In the figure,
The same reference numerals as those in FIG. 20 denote the same or corresponding parts, and reference numeral 34 denotes a charged particle, that is, an ion or an electron, from the supersonic molecular flow E of plasma in the second vacuum chamber 23. Is a pair of charged particle removing electrodes for forming a supersonic molecular flow F of neutral atomic molecular gas, 35 is a DC voltage applying means for applying a voltage between the pair of electrodes 34, The charged particle removing means is constituted by the DC voltage applying means and the DC voltage applying means. G is a supersonic molecular flow of the neutral atomic molecular gas which has flowed into the third vacuum chamber 24 after passing through the collimator 30 in the supersonic molecular flow F of the neutral atomic molecular gas, The substrate 1 to be etched is disposed on the electrode 2 in the third vacuum chamber 24 so as to face the supersonic molecular flow G.

 Next, the operation will be described.

The mixed gas of the etching gas A and the light element gas B is ionized in the discharge chamber 21 and the ionized gas is
The supersonic free jet D is formed by the supersonic free jet D in the vacuum chamber 22 of FIG.
Since the process up to the point where the supersonic molecular flow E of the plasma is extracted into the second vacuum chamber 23 is the same as in the sixth embodiment, its description is omitted.

In the second vacuum chamber 23, a pair of charged particle removing electrodes 34 is disposed so as to sandwich the supersonic molecular flow E of plasma, and a DC voltage applying means is provided between the pair of electrodes 34. 35
, And an electric field is generated in a direction perpendicular to the flow direction of the supersonic molecular flow E. Accordingly, the ions and electrons of the supersonic molecular flow E of the plasma flowing between the pair of electrodes 34 are separated and moved in directions opposite to each other by an electric field perpendicular to the direction of the flow of the supersonic molecular flow E. It is captured by the pair of electrodes 34. As a result, the charged particle removing electrode 34
The ions and electrons are removed from the supersonic molecular flow E of the plasma that has passed, and a supersonic molecular flow F of a neutral atomic molecular gas is extracted.

In the supersonic molecular flow F of the neutral atomic molecular gas generated in this way, the gas temperature is extremely low at several degrees or less in absolute temperature as in the case of the supersonic molecular flow E of the plasma. The thermal velocity is extremely low and the interaction between particles is negligible. The supersonic molecular flow F of the neutral atomic molecular gas having such characteristics passes through the collimator 30 arranged on the second partition wall 29 and flows into the third vacuum chamber 24. Note here similar to the embodiment of the opening diameter of the collimator 30 the sixth, or less opening diameter about the same skimmer 28 and the vacuum degree of the third vacuum chamber 24 is ^{10-8 - 7} Torr
Degree, which is indicated by the third vacuum gauge 13.

Then, in the third vacuum chamber 24, the supersonic molecular flow G of the neutral atomic molecular gas flowing through the collimator 30 flows.
Is vertically sprayed on the substrate 1 to be etched placed on the electrode 2.

As described above, the substrate 1 to be etched has a gas temperature extremely low as several degrees or less in absolute temperature, that is, a reactive neutral atom gas in which the thermal motion velocity of neutral atom molecules is extremely small and the interaction between particles can be ignored. Is sprayed, the neutral atomic radicals of the reactive neutral atomic gas are perpendicularly incident on the substrate surface as a low-temperature low-energy reactive particle beam. Therefore, the velocity component of the neutral atomic molecular radical in the horizontal direction with respect to the substrate surface is extremely smaller than the incident speed in the vertical direction, and the incident energy is much smaller than the physical sputtering threshold.

FIG. 27 is a schematic diagram for explaining a mechanism in which a substance on a substrate disposed opposite to a supersonic molecular flow of a neutral atomic molecular gas is etched in the dry etching apparatus of the seventh embodiment. is there. In the apparatus of this embodiment, since etching is performed using a neutral atomic molecule gas instead of plasma, a space charge region (sheath) is not formed near the substrate, and there is no contribution to ion etching. On the other hand, the neutral atomic molecular radicals are perpendicularly incident on the substrate surface in the state of supersonic molecular flow, so the chemical etching of the substance on the substrate by the neutral radicals becomes anisotropic. Gives sex at the same time.

Therefore, in the dry etching apparatus of this embodiment, the etching of the substance on the substrate proceeds only by the anisotropic chemical etching caused by the neutral radicals incident on the substrate surface at a high speed. Etching that simultaneously satisfies both selectivity and extremely low damageability is performed.

Here, the supersonic molecular flow F of neutral atomic molecular gas generated by removing ions and electrons from the supersonic molecular flow E of plasma contains Cl as atomic radicals and has a gas density of 10 ¹² to 10 ¹⁵ cm. It is about ^-3 . When the gas temperature of the discharge chamber 21 is T ₀ = 10 ⁴ K and the mixing ratio of chlorine gas and helium gas is about 5% or less, as described in the sixth embodiment, the supersonic molecular flow is reduced. The upper limit of the velocity in the flow direction is (5 kT ₀ / M _He ) ^1/2 ≒ 1 × 10 ⁶ cm / sec, and the kinetic energies for He and Cl correspond to about 2 eV and 19 eV, respectively.

As described above, according to the present embodiment, the plasma 10 of the mixed gas of the etching gas A and the light element gas B generated by the discharge is supersonic expanded into the first vacuum chamber 22 through the nozzle 26, and the plasma A supersonic free jet D is formed, and then a supersonic molecular flow E of plasma having a very low gas temperature and negligible interaction between heavy particles is introduced into the second vacuum chamber 23 through the skimmer 28 from the supersonic free jet D. Extraction and further removal of ions and electrons from the supersonic molecular stream E of the plasma by means of charged particle removal means that the gas temperature is extremely low, that is, the thermal motion velocity of neutral atomic molecules is extremely small and the interaction between particles is ignored. Since the supersonic molecular flow F of the generated neutral atomic molecule gas is blown onto the substrate 1 to be etched through the collimator 30, the neutral atomic molecules emit a low-temperature low-energy particle beam. It will be perpendicularly incident on the substrate surface.

In this case, the velocity component of the neutral atomic molecular radical in the horizontal direction with respect to the substrate surface is extremely small as compared with the incident velocity in the vertical direction, and the incident energy is much smaller than the physical sputtering threshold. In addition, when the mixing ratio of the reactive gas to the light element gas is reduced, the incident velocity of neutral radicals on the reactive gas in the direction perpendicular to the substrate surface becomes substantially equal to the incident velocity of atomic molecules on the light element gas. Faster. Therefore, the etching of the substance on the substrate proceeds only by the more anisotropic chemical etching due to the fast neutral atomic molecular radical, and thereby, not only ultra-high anisotropy but also ultra-high selectivity and ultra-low damage property are simultaneously obtained. There is an effect that satisfactory high-speed etching can be realized.

In addition, since the etching is performed by neutral atomic molecular radicals, there is also an effect that electrostatic destruction due to charging (charge-up) of the substrate to be etched by charged particles can be prevented.

In the seventh embodiment, ions and electrons of the supersonic molecular stream E of plasma are removed by the charged particle removing electrode 34 installed in the second vacuum chamber 23, and the supersonic molecular stream of neutral atomic molecular gas is removed. Although the case where the flow F is taken out has been described,
The charged particle removing electrode 34 may be provided in the third vacuum chamber 24. In that case, the supersonic molecular flow E of the plasma is a collimator
After passing through 30 and flowing into the third vacuum chamber 24, the third vacuum chamber
In 24, ions and electrons are removed from the supersonic molecular flow of the plasma, and a supersonic molecular flow of neutral atomic molecular gas is extracted.

In the seventh embodiment, the case where only the electric field is used for the charged particle removing means has been described. However, both the electric field and the magnetic field may be used.

FIG. 28 is a cross-sectional configuration diagram for explaining a configuration using an electric field and a magnetic field. In this configuration, a pair of electrodes 34a having an opening at the center are installed so as to face the supersonic molecular flow E of plasma, DC voltage applying means 3 is provided between the pair of electrodes 34a.
A voltage is applied by 5 to generate an electric field parallel to the flow direction of the supersonic molecular flow E.

In this case, the ions and electrons of the supersonic molecular flow E of the plasma flowing between the pair of electrodes 34a are separated in opposite directions by an electric field parallel to the flow direction of the supersonic molecular flow.
The supersonic molecular flow is moved and further removed from the supersonic molecular flow by the magnetic field applying means 43a using a permanent magnet or an electromagnetic coil installed following the pair of electrodes 34a, and the supersonic molecular flow F is taken out. Here, the polarity of the DC voltage applying means 35 is negative, and the magnetic field applying means 43a is
The direction of the magnetic field due to is the γ direction perpendicular to the direction of the flow of the supersonic molecular flow, and I is the ion flow turned by the magnetic field γ.

Next, an eighth embodiment of the present invention will be described. No. 29
FIG. 13 is a partial sectional view showing the vicinity of a discharge chamber 21 in a dry etching apparatus according to an eighth embodiment of the present invention. In the figures, the same reference numerals as those in FIGS. 20 and 26 indicate the same or corresponding parts. The discharge chamber 21 is divided into two chambers, a first chamber for introducing a light element gas B such as helium or hydrogen and ionizing the light element gas, and a first chamber for introducing the ionized gas and further introducing an etching gas A. A second chamber 51 for mixing both gases is provided, and these first and second chambers are connected through an opening 56.

 Next, the operation will be described.

Light element gas B such as helium or hydrogen is introduced into the first chamber of the discharge chamber 21 to ionize the light element gas. The ionized gas of the light element passes through the opening 56 and flows into the second chamber 51, where it is mixed with the etching gas A. As a result, ionization and dissociation of the etching gas atoms and molecules are not direct discharges,
Interaction with the light element gas plasma generated by the direct discharge, that is, the collision occurs between the light element gas atom molecules or plasma electrons generated and excited by the ionization or dissociation by the discharge and the plasma gas electrons and the etching gas atom molecules. Accordingly, the amount of neutral radicals generated by the dissociation of the reactive gas atom molecules is larger than in the case of direct discharge, and the degree of corrosion and damage of the discharge chamber due to the direct discharge of reactive gas is also reduced. .

The supersonic molecular flow of the plasma extracted from the plasma thus generated, or the supersonic molecular flow of a neutral atomic molecular gas obtained by removing ions and electrons from the supersonic molecular flow of the plasma by the above-described charged particle removing means. Is sprayed onto the substrate to be etched, so that etching that simultaneously satisfies ultra-high anisotropy, ultra-high selectivity, and ultra-low damage can be obtained at a higher speed, and the deterioration of the discharge chamber is suppressed. This has the effect of extending the life.

In the sixth, seventh, and eighth embodiments, the generation of the plasma in the discharge chamber 21 is performed by a high-frequency induction glow discharge using RF or an arc discharge, that is, the coil 14 installed outside the discharge chamber 21. Although the case where the high-frequency electric field is indirectly induced in the inside by the method described above is explained, this is the case where the plasma is generated.
RF or microwave high-frequency glow discharge or arc discharge is used. That is, a counter electrode or an antenna is arranged in the discharge chamber 21, thereby generating a high-frequency electric field directly in the discharge chamber to generate plasma. Or microwave beam, electron beam,
A configuration in which plasma is generated by beam irradiation ionization using an ion beam, a neutral particle beam, a laser beam, or the like may be employed.

Further, in each of the above embodiments, the case where chlorine is used as the etching gas A to etch the polycrystalline silicon on the substrate 1 to be etched has been described. However, other etching gases may be selected. The material to be etched may be etched by selecting an appropriate etching gas.

Furthermore, in each of the above embodiments, the case where the frequency of the RF applying means 6 and 43 is 13.56 MHz has been described, but other frequencies may be used.

On the other hand, in each of the above embodiments, the case where helium is used as the light element gas B has been described, but hydrogen or the like may be used.

Further, in each of the above embodiments, the case where the frequency of the RF power applying means 6 and 43 is 13.56 MHz has been described, but other frequencies may be used.

Furthermore, in each of the above embodiments, the opening diameter of the nozzle 26 is 1 m.
m, but the first evacuation means 3
The pumping speed of (1) is increased to make the opening diameter of the nozzle 26 larger than about 1 mm, and the pumping speed of the second vacuum pumping means 32 is further increased to adjust the opening diameter of the skimmer 28 to the opening diameter of the nozzle 26. May be larger.

In this case, in the apparatus of the sixth embodiment, the flux of the supersonic molecular stream E of the plasma extracted through the skimmer 28 increases,
By increasing the evacuation speed of the third evacuation means 33 to increase the opening diameter of the collimator 30, the area to be etched and the etching speed on the substrate 1 to be etched are increased.

In the seventh embodiment, the supersonic molecular flow E of the plasma extracted from the skimmer 28 and the supersonic molecular flow F of the neutral atomic molecular gas extracted through the charged particle removing electrode 34 are extracted. And the diameter of the collimator 30 is increased by increasing the pumping speed of the third vacuum pumping means 33, thereby increasing the area to be etched on the substrate 1 to be etched and the etching rate.

Further, in the device of the eighth embodiment, the same effect as that in the device of the sixth embodiment or the device of the seventh embodiment can be obtained.

〔The invention's effect〕

As described above, according to the dry etching apparatus according to the first aspect of the present invention, a dry etching apparatus that introduces a source gas and etches a material to be etched has an ejection nozzle that ejects a generated gas. A discharge chamber for ionizing atomic molecules of the raw material gas to generate plasma, and introducing the plasma into the interior through the jet nozzle, and supersonic expansion of the plasma to form a supersonic free jet. A first vacuum chamber, and a second vacuum chamber for introducing a supersonic molecular flow having a skimmer for extracting a supersonic molecular flow from a supersonic free jet of the plasma.
The supersonic molecular flow of the plasma taken out of the vacuum chamber is blown onto the material to be etched, so that etching that satisfies both ultra-high anisotropy, ultra-high selectivity and ultra-low damage simultaneously can be realized. effective.

Further, according to the dry etching apparatus according to the second aspect of the present invention, in the dry etching apparatus for etching a material to be etched by introducing a raw material gas, the dry etching apparatus has a jet nozzle for jetting a generated gas, A discharge chamber for generating plasma by ionizing the atomic molecules of the above, and a first chamber for introducing the plasma into the interior through the ejection nozzle and supersonic expansion to form a supersonic free jet. A vacuum chamber, a skimmer for extracting a supersonic molecular flow of the plasma from the supersonic free jet of the plasma, a second vacuum chamber for introducing the supersonic molecular flow, and a second vacuum chamber for introducing the supersonic molecular flow. Charged particle removing means for removing ions and electrons from the supersonic molecular flow of the extracted plasma to form a supersonic molecular flow of a neutral atomic molecular gas, wherein the supersonic molecular flow of the neutral atomic molecular gas is provided. To Since the material to be etched is sprayed, it is possible to simultaneously satisfy ultra-high anisotropy, ultra-high selectivity and ultra-low damage of etching, and prevent electrostatic breakdown due to charge-up of the substrate to be etched. There is an effect that can be.

Further, according to the dry etching apparatus according to the invention of claim 3 of the present application, in a dry etching apparatus using discharge of reactive gas atom molecules, a discharge chamber for generating plasma, and a plasma generated in the discharge chamber are superposed. A two-dimensional nozzle having a rectangular slit-shaped opening section for sonic expansion, a first vacuum chamber, and a supersonic free-expanding plasma formed in the first vacuum chamber from the discharge chamber through the nozzle. A two-dimensional skimmer having a rectangular slit-shaped opening section for extracting a supersonic molecular flow from a sonic free jet, and a second vacuum chamber; and passing through the skimmer from the first vacuum chamber to the second vacuum chamber. The supersonic molecular flow of the plasma extracted to the substrate is sprayed on the substrate to be etched, so that it has not only ultra-high anisotropy but also ultra-high selectivity and ultra-low damage. There is a current can be effectively.

Further, according to the dry etching apparatus according to the invention of claim 4 of the present application, in a dry etching apparatus using discharge of reactive gas atomic molecules, a discharge chamber for generating plasma, and a plasma generated in the discharge chamber is superposed. A supersonic velocity of a plasma formed by supersonic free-expansion into the first vacuum chamber from the discharge chamber through the nozzle, a two-dimensional nozzle having a rectangular slit-shaped cross section, and a first slit formed in the first vacuum chamber. A two-dimensional skimmer having a rectangular slit-shaped opening section for extracting a supersonic molecular flow from the free jet, a second vacuum chamber, and the second vacuum chamber through the skimmer from the first vacuum chamber.
Means for removing charged particles from the supersonic molecular flow of the plasma taken out into the vacuum chamber, wherein ions and ions are removed by the charged particle removing means from the supersonic molecular flow of the plasma taken out into the second vacuum chamber. The supersonic molecular flow of the neutral atomic molecular gas from which the electrons have been removed is blown onto the substrate to be etched to perform the etching.
Not only is it possible to perform etching that simultaneously satisfies ultra-high selectivity and ultra-low damage, but also it is possible to prevent electrostatic destruction due to charging (charge-up) of the substrate to be etched by charged particles. is there.

Further, according to the dry etching apparatus of the fifth aspect of the present invention, in the dry etching apparatus of the third or fourth aspect, the position of the substrate to be etched has a rectangular slit-shaped cross section perpendicular to the flow. Etching is performed while moving the supersonic molecular flow, which becomes a sheet-like beam, relatively in the direction of its short side, so that it simultaneously satisfies ultra-high anisotropy, ultra-high selectivity and ultra-low damage This has the effect that a large-diameter substrate can be etched.

Further, according to the dry etching apparatus according to the invention of claim 6 of the present application, in a dry etching apparatus using discharge of reactive gas atomic molecules, a discharge chamber for generating plasma and a plasma generated in the discharge chamber are super-charged. A nozzle for sonic expansion, a first vacuum chamber, and a supersonic free jet of plasma formed by supersonic free expansion in the first vacuum chamber through the nozzle from the discharge chamber to extract a supersonic molecular flow. A skimmer and a second vacuum chamber are provided, a reactive gas and a light element gas such as helium or hydrogen are introduced into the discharge chamber to ionize the mixed gas, and pass through the skimmer from the first vacuum chamber. The supersonic molecular flow of the plasma taken out into the second vacuum chamber is blown onto the substrate to be etched, so that etching is performed. There is an effect that can realize etching which satisfies simultaneously the ultra low damage resistance at high speed.

Further, according to the dry etching apparatus according to the invention of claim 7 of the present application, in a dry etching apparatus using discharge of reactive gas atomic molecules, a discharge chamber for generating plasma and a plasma generated in the discharge chamber are superposed. A nozzle for sonic expansion, a first vacuum chamber, and a skimmer for extracting a supersonic molecular flow from a supersonic free jet of plasma formed by supersonic free expansion from the discharge chamber into the first vacuum chamber through the nozzle. And a second vacuum chamber; and means for removing charged particles from a supersonic molecular flow of plasma taken out of the first vacuum chamber through the skimmer into the second vacuum chamber, and reacting with the discharge chamber. Ionic gas and a light element gas such as helium or hydrogen are introduced to ionize the mixed gas, and the charged gas is extracted from the supersonic molecular flow of the plasma taken out into the second vacuum chamber. The supersonic molecular flow of neutral atomic molecular gas from which ions and electrons have been removed by the electron removal means is sprayed onto the substrate to be etched, so that etching is performed, resulting in ultra-high anisotropy, ultra-high selectivity, and ultra-low damage. In addition to the high-speed etching that simultaneously satisfies the properties, it is possible to prevent electrostatic destruction due to charging (charge-up) of the substrate to be etched.

According to the dry etching apparatus according to the invention of claim 8 of the present application, in the dry etching apparatus according to claim 6 or 7, the discharge chamber is divided into two chambers, and a light element gas such as helium or hydrogen is introduced. Therefore, a first chamber for ionizing the light element gas and a second chamber for introducing the plasma generated by the ionization and introducing the reactive gas to mix the two gases are provided. Etching that satisfies anisotropy, ultra-high selectivity and ultra-low damage simultaneously can be obtained at a higher speed, and there is an effect that deterioration of the discharge chamber can be suppressed and the life can be extended.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a configuration of a dry etching apparatus according to a first embodiment of the present invention, FIG. 2 is a sectional view showing details of a supersonic free jet shown in FIG. 1, and FIG. FIG. 4 is a view showing an example of a continuously variable mechanism of a distance between a nozzle and a skimmer of the apparatus of this embodiment. FIG. 4 is a schematic view showing a state in which plasma constituent particles are incident on the surface of the substrate to be etched in the apparatus of this embodiment. FIG. 6 is a partial cross-sectional view showing a case where RF power applying means for applying RF power to an electrode for mounting a substrate to be etched of the apparatus of the present embodiment is provided. FIG. 6 is a schematic cross-sectional view showing a conventional dry etching apparatus. FIG. 8 is a schematic view showing a state in which plasma constituent particles are incident on the surface of an etching substrate in a conventional apparatus. FIG. 8 is a cross-sectional view of a main part showing a configuration of a dry etching apparatus according to a second embodiment of the present invention. The dry edge of the second embodiment FIG. 10 is a schematic view showing a state in which neutral atoms and molecules are incident on the surface of an etching substrate during etching in a chucking device. FIG. 10 is a diagram showing charged particles for removing charged particles using an electric field and a magnetic field in the second embodiment. FIG. 11 is a cross-sectional view showing a configuration of a removing unit. FIG.
FIG. 12 is a cross-sectional view showing details of the supersonic free jet shown in FIG. 11, FIG. 13 is a cross-sectional view showing an example of a continuously variable nozzle-skimmer distance mechanism of the apparatus of the present embodiment, and FIG. FIG. 15 is a schematic view showing a state where constituent particles of plasma are incident on a substrate to be etched in the apparatus of the embodiment, and FIG. 15 shows a case where a unit for applying RF power is provided to the electrode for mounting the substrate to be etched in the apparatus of the embodiment. FIG. 16 is a partial sectional view showing a configuration of a dry etching apparatus according to a fourth embodiment of the present invention, and FIG. 17 is a schematic view showing a neutral atom molecule incident on a substrate to be etched in the apparatus according to the fourth embodiment. FIG. 18 is a partial cross-sectional view showing a case where charged particles are removed by using an electric field and a magnetic field in the apparatus of the fourth embodiment, and FIG. 19 is a fifth embodiment of the present invention. In the apparatus, the position of the substrate to be etched Schematic sectional view showing a state of moving the manner, FIG. 20 sixth cross sectional view showing a structure of a dry etching apparatus according to an embodiment of the present invention, FIG. 21 No.
FIG. 20 is a cross-sectional view showing details of the supersonic free jet, FIG. 22 is a detailed view showing the flow characteristics in the quiet region of the supersonic free jet shown in FIG. 21, and FIG. 23 is a nozzle of the apparatus of the present embodiment. −
Sectional view showing an example of a continuously variable mechanism of the distance between skimmers, FIG.
FIG. 24 is a schematic view showing a state in which the constituent particles of the plasma are incident on the substrate to be etched in the apparatus of the present embodiment, and FIG. 25 is a diagram showing a means for applying RF power to the electrode for mounting the substrate to be etched in the apparatus of the present embodiment. FIG. 26 is a partial cross-sectional view showing a case where a neutral atom molecule is provided in a dry etching apparatus according to a seventh embodiment of the present invention. FIG. FIG. 28 is a schematic view showing a state of incidence on a substrate, FIG. 28 is a partial cross-sectional view showing a case where charged particles are removed using an electric field and a magnetic field in the seventh embodiment, and FIG. FIG. 18 is a partial cross-sectional view showing a case where the discharge chamber is divided into two chambers in the apparatus of Example 8; In the figure, 1 is a substrate to be etched, 21 is a discharge chamber, 22 is a first vacuum chamber, 23 is a second vacuum chamber, 26 and 26a are nozzles, 2
8, 28a are skimmers, 34 is an electrode for removing charged particles, 35 is DC voltage applying means, 41 is a mechanism for continuously varying the distance between the nozzle and skimmer, 43 is RF power applying means, 43a is magnetic field applying means, and 51 is etching gas mixing. The chamber, A is an etching gas, B is a light element gas, D is a supersonic free jet of ionized gas, E is a supersonic molecular flow of ionized gas, and F is a supersonic molecular flow of neutral atomic molecular gas. In the drawings, the same reference numerals indicate the same or corresponding parts.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-205720 (JP, A) JP-A-61-150322 (JP, A) JP-A-61-42135 (JP, A) JP-A-63 124528 (JP, A) JP-A-61-163287 (JP, A) JP-A-52-77840 (JP, A)

Claims (8)

(57) [Claims] 1. A dry etching apparatus for etching a material to be etched by introducing a source gas, comprising: a jet nozzle for jetting a generated gas; for generating plasma by ionizing atomic molecules of the source gas. A first vacuum chamber for introducing the plasma into the interior through the ejection nozzle and supersonic expansion to form a supersonic free jet; and a supersonic free jet of the plasma. A second vacuum chamber for introducing the supersonic molecular flow; and a second vacuum chamber for introducing the supersonic molecular flow. A dry etching apparatus characterized by spraying on an etching material. 2. A dry etching apparatus for etching a material to be etched by introducing a source gas, comprising: a jet nozzle for jetting a generated gas; and for generating plasma by ionizing atomic molecules of the source gas. A discharge chamber, a first vacuum chamber for introducing the plasma into the interior through the ejection nozzle, and supersonic expansion of the plasma to form a supersonic free jet; and a plasma from the supersonic free jet of the plasma. A second vacuum chamber for introducing the supersonic molecular flow, and ions and electrons from the supersonic molecular flow of the plasma taken out into the second vacuum chamber. And a charged particle removing means for forming a supersonic molecular flow of a neutral atomic molecular gas by spraying the supersonic molecular flow of the neutral atomic molecular gas onto the material to be etched. Dry etching apparatus according to claim. 3. A dry etching apparatus using discharge of reactive gas atom molecules, comprising: a discharge chamber for generating plasma; and a rectangular slit-shaped opening section for supersonic expansion of the plasma generated in the discharge chamber. Dimensional nozzle and first
Extracting a supersonic molecular flow from a supersonic free jet of plasma formed by supersonic free expansion into the first vacuum chamber through the nozzle from the discharge chamber, the opening having a rectangular cross section. A two-dimensional skimmer and a second vacuum chamber, wherein a supersonic molecular flow of plasma taken out of the first vacuum chamber through the skimmer into the second vacuum chamber is blown onto the substrate to be etched. A dry etching apparatus characterized in that etching is performed by using a dry etching method. 4. A dry etching apparatus using discharge of reactive gas atom molecules, comprising: a discharge chamber for generating plasma; and a rectangular slit-shaped opening section for supersonic expansion of the plasma generated in the discharge chamber. Dimensional nozzle and first
Extracting a supersonic molecular flow from a supersonic free jet of plasma formed by supersonic free expansion from the discharge chamber through the nozzle into the first vacuum chamber, the opening having a rectangular slit shape. A two-dimensional skimmer, a second vacuum chamber, and means for removing charged particles from a supersonic molecular flow of plasma taken out of the first vacuum chamber through the skimmer into the second vacuum chamber, From the supersonic molecular flow of the plasma taken out into the second vacuum chamber, the supersonic molecular flow of neutral atomic molecular gas from which ions and electrons have been removed by the charged particle removing means is blown onto the substrate to be etched to perform etching. Dry etching apparatus characterized by performing. 5. The dry etching apparatus according to claim 3, wherein the position of the substrate to be etched is changed with respect to a supersonic molecular flow in which a cross-sectional shape perpendicular to the flow is a sheet beam having a rectangular slit shape. A dry etching apparatus characterized in that etching is performed while moving relatively in the direction of the short side. 6. A dry etching apparatus using discharge of reactive gas atomic molecules, comprising: a discharge chamber for generating plasma; a nozzle for supersonic expansion of the plasma generated in the discharge chamber; and a first vacuum chamber; A skimmer for extracting a supersonic molecular flow from a supersonic free jet of plasma formed by supersonic free expansion from the discharge chamber through the nozzle into the first vacuum chamber, and a second vacuum chamber; A reactive gas and a light element gas such as helium or hydrogen are introduced into the chamber to ionize the mixed gas, and the plasma taken out from the first vacuum chamber through the skimmer into the second vacuum chamber. Supersonic molecular flow,
A dry etching apparatus for performing etching by spraying on a substrate to be etched. 7. A dry etching apparatus using discharge of reactive gas atom molecules, comprising: a discharge chamber for generating plasma; a nozzle for supersonic expansion of the plasma generated in the discharge chamber; and a first vacuum chamber; A skimmer for extracting a supersonic molecular flow from a supersonic free jet of plasma formed by supersonic free expansion from the discharge chamber through the nozzle into the first vacuum chamber, a second vacuum chamber, and the first vacuum Means for removing charged particles from a supersonic molecular flow of plasma taken out of the chamber through the skimmer and into the second vacuum chamber, wherein a reactive gas and a light element gas such as helium or hydrogen are supplied to the discharge chamber. The mixed gas is introduced and ionized to remove ions and electrons from the supersonic molecular flow of the plasma taken out into the second vacuum chamber by the charged particle removing means. The supersonic molecular flow of atoms and molecules gas, a dry etching apparatus and performing etching by spraying the etching target substrate. 8. The dry etching apparatus according to claim 6, wherein the discharge chamber is divided into two chambers, and a first chamber for introducing a light element gas such as helium or hydrogen and ionizing the light element gas; A dry etching apparatus comprising: a second chamber into which the plasma generated by the ionization flows, and into which a reactive gas is further introduced to mix the two gases.